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/*------------------------------------------------------------------------- * * relation.h * Definitions for planner's internal data structures. * * * Portions Copyright (c) 1996-2012, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * * src/include/nodes/relation.h * *------------------------------------------------------------------------- */ #ifndef RELATION_H #define RELATION_H #include "access/sdir.h" #include "nodes/params.h" #include "nodes/parsenodes.h" #include "storage/block.h" /* * Relids * Set of relation identifiers (indexes into the rangetable). */ typedef Bitmapset *Relids; /* * When looking for a "cheapest path", this enum specifies whether we want * cheapest startup cost or cheapest total cost. */ typedef enum CostSelector { STARTUP_COST, TOTAL_COST } CostSelector; /* * The cost estimate produced by cost_qual_eval() includes both a one-time * (startup) cost, and a per-tuple cost. */ typedef struct QualCost { Cost startup; /* one-time cost */ Cost per_tuple; /* per-evaluation cost */ } QualCost; /* * Costing aggregate function execution requires these statistics about * the aggregates to be executed by a given Agg node. Note that transCost * includes the execution costs of the aggregates' input expressions. */ typedef struct AggClauseCosts { int numAggs; /* total number of aggregate functions */ int numOrderedAggs; /* number that use DISTINCT or ORDER BY */ QualCost transCost; /* total per-input-row execution costs */ Cost finalCost; /* total costs of agg final functions */ Size transitionSpace; /* space for pass-by-ref transition data */ } AggClauseCosts; /*---------- * PlannerGlobal * Global information for planning/optimization * * PlannerGlobal holds state for an entire planner invocation; this state * is shared across all levels of sub-Queries that exist in the command being * planned. *---------- */ typedef struct PlannerGlobal { NodeTag type; ParamListInfo boundParams; /* Param values provided to planner() */ List *paramlist; /* unused, will be removed in 9.3 */ List *subplans; /* Plans for SubPlan nodes */ List *subroots; /* PlannerInfos for SubPlan nodes */ Bitmapset *rewindPlanIDs; /* indices of subplans that require REWIND */ List *finalrtable; /* "flat" rangetable for executor */ List *finalrowmarks; /* "flat" list of PlanRowMarks */ List *resultRelations; /* "flat" list of integer RT indexes */ List *relationOids; /* OIDs of relations the plan depends on */ List *invalItems; /* other dependencies, as PlanInvalItems */ Index lastPHId; /* highest PlaceHolderVar ID assigned */ Index lastRowMarkId; /* highest PlanRowMark ID assigned */ bool transientPlan; /* redo plan when TransactionXmin changes? */ /* Added post-release, will be in a saner place in 9.3: */ int nParamExec; /* number of PARAM_EXEC Params used */ } PlannerGlobal; /* macro for fetching the Plan associated with a SubPlan node */ #define planner_subplan_get_plan(root, subplan) \ ((Plan *) list_nth((root)->glob->subplans, (subplan)->plan_id - 1)) /*---------- * PlannerInfo * Per-query information for planning/optimization * * This struct is conventionally called "root" in all the planner routines. * It holds links to all of the planner's working state, in addition to the * original Query. Note that at present the planner extensively modifies * the passed-in Query data structure; someday that should stop. *---------- */ typedef struct PlannerInfo { NodeTag type; Query *parse; /* the Query being planned */ PlannerGlobal *glob; /* global info for current planner run */ Index query_level; /* 1 at the outermost Query */ struct PlannerInfo *parent_root; /* NULL at outermost Query */ /* * simple_rel_array holds pointers to "base rels" and "other rels" (see * comments for RelOptInfo for more info). It is indexed by rangetable * index (so entry 0 is always wasted). Entries can be NULL when an RTE * does not correspond to a base relation, such as a join RTE or an * unreferenced view RTE; or if the RelOptInfo hasn't been made yet. */ struct RelOptInfo **simple_rel_array; /* All 1-rel RelOptInfos */ int simple_rel_array_size; /* allocated size of array */ /* * simple_rte_array is the same length as simple_rel_array and holds * pointers to the associated rangetable entries. This lets us avoid * rt_fetch(), which can be a bit slow once large inheritance sets have * been expanded. */ RangeTblEntry **simple_rte_array; /* rangetable as an array */ /* * all_baserels is a Relids set of all base relids (but not "other" * relids) in the query; that is, the Relids identifier of the final join * we need to form. This is computed in make_one_rel, just before we * start making Paths. */ Relids all_baserels; /* * join_rel_list is a list of all join-relation RelOptInfos we have * considered in this planning run. For small problems we just scan the * list to do lookups, but when there are many join relations we build a * hash table for faster lookups. The hash table is present and valid * when join_rel_hash is not NULL. Note that we still maintain the list * even when using the hash table for lookups; this simplifies life for * GEQO. */ List *join_rel_list; /* list of join-relation RelOptInfos */ struct HTAB *join_rel_hash; /* optional hashtable for join relations */ /* * When doing a dynamic-programming-style join search, join_rel_level[k] * is a list of all join-relation RelOptInfos of level k, and * join_cur_level is the current level. New join-relation RelOptInfos are * automatically added to the join_rel_level[join_cur_level] list. * join_rel_level is NULL if not in use. */ List **join_rel_level; /* lists of join-relation RelOptInfos */ int join_cur_level; /* index of list being extended */ List *init_plans; /* init SubPlans for query */ List *cte_plan_ids; /* per-CTE-item list of subplan IDs */ List *eq_classes; /* list of active EquivalenceClasses */ List *canon_pathkeys; /* list of "canonical" PathKeys */ List *left_join_clauses; /* list of RestrictInfos for * mergejoinable outer join clauses * w/nonnullable var on left */ List *right_join_clauses; /* list of RestrictInfos for * mergejoinable outer join clauses * w/nonnullable var on right */ List *full_join_clauses; /* list of RestrictInfos for * mergejoinable full join clauses */ List *join_info_list; /* list of SpecialJoinInfos */ List *append_rel_list; /* list of AppendRelInfos */ List *rowMarks; /* list of PlanRowMarks */ List *placeholder_list; /* list of PlaceHolderInfos */ List *query_pathkeys; /* desired pathkeys for query_planner(), and * actual pathkeys after planning */ List *group_pathkeys; /* groupClause pathkeys, if any */ List *window_pathkeys; /* pathkeys of bottom window, if any */ List *distinct_pathkeys; /* distinctClause pathkeys, if any */ List *sort_pathkeys; /* sortClause pathkeys, if any */ List *minmax_aggs; /* List of MinMaxAggInfos */ List *initial_rels; /* RelOptInfos we are now trying to join */ MemoryContext planner_cxt; /* context holding PlannerInfo */ double total_table_pages; /* # of pages in all tables of query */ double tuple_fraction; /* tuple_fraction passed to query_planner */ double limit_tuples; /* limit_tuples passed to query_planner */ bool hasInheritedTarget; /* true if parse->resultRelation is an * inheritance child rel */ bool hasJoinRTEs; /* true if any RTEs are RTE_JOIN kind */ bool hasHavingQual; /* true if havingQual was non-null */ bool hasPseudoConstantQuals; /* true if any RestrictInfo has * pseudoconstant = true */ bool hasRecursion; /* true if planning a recursive WITH item */ /* These fields are used only when hasRecursion is true: */ int wt_param_id; /* PARAM_EXEC ID for the work table */ struct Plan *non_recursive_plan; /* plan for non-recursive term */ /* These fields are workspace for createplan.c */ Relids curOuterRels; /* outer rels above current node */ List *curOuterParams; /* not-yet-assigned NestLoopParams */ /* optional private data for join_search_hook, e.g., GEQO */ void *join_search_private; /* Added post-release, will be in a saner place in 9.3: */ List *plan_params; /* list of PlannerParamItems, see below */ /* This will be in a saner place in 9.4: */ Relids nullable_baserels; } PlannerInfo; /* * In places where it's known that simple_rte_array[] must have been prepared * already, we just index into it to fetch RTEs. In code that might be * executed before or after entering query_planner(), use this macro. */ #define planner_rt_fetch(rti, root) \ ((root)->simple_rte_array ? (root)->simple_rte_array[rti] : \ rt_fetch(rti, (root)->parse->rtable)) /*---------- * RelOptInfo * Per-relation information for planning/optimization * * For planning purposes, a "base rel" is either a plain relation (a table) * or the output of a sub-SELECT or function that appears in the range table. * In either case it is uniquely identified by an RT index. A "joinrel" * is the joining of two or more base rels. A joinrel is identified by * the set of RT indexes for its component baserels. We create RelOptInfo * nodes for each baserel and joinrel, and store them in the PlannerInfo's * simple_rel_array and join_rel_list respectively. * * Note that there is only one joinrel for any given set of component * baserels, no matter what order we assemble them in; so an unordered * set is the right datatype to identify it with. * * We also have "other rels", which are like base rels in that they refer to * single RT indexes; but they are not part of the join tree, and are given * a different RelOptKind to identify them. Lastly, there is a RelOptKind * for "dead" relations, which are base rels that we have proven we don't * need to join after all. * * Currently the only kind of otherrels are those made for member relations * of an "append relation", that is an inheritance set or UNION ALL subquery. * An append relation has a parent RTE that is a base rel, which represents * the entire append relation. The member RTEs are otherrels. The parent * is present in the query join tree but the members are not. The member * RTEs and otherrels are used to plan the scans of the individual tables or * subqueries of the append set; then the parent baserel is given Append * and/or MergeAppend paths comprising the best paths for the individual * member rels. (See comments for AppendRelInfo for more information.) * * At one time we also made otherrels to represent join RTEs, for use in * handling join alias Vars. Currently this is not needed because all join * alias Vars are expanded to non-aliased form during preprocess_expression. * * Parts of this data structure are specific to various scan and join * mechanisms. It didn't seem worth creating new node types for them. * * relids - Set of base-relation identifiers; it is a base relation * if there is just one, a join relation if more than one * rows - estimated number of tuples in the relation after restriction * clauses have been applied (ie, output rows of a plan for it) * width - avg. number of bytes per tuple in the relation after the * appropriate projections have been done (ie, output width) * reltargetlist - List of Var and PlaceHolderVar nodes for the values * we need to output from this relation. * List is in no particular order, but all rels of an * appendrel set must use corresponding orders. * NOTE: in a child relation, may contain RowExpr or * ConvertRowtypeExpr representing a whole-row Var. * pathlist - List of Path nodes, one for each potentially useful * method of generating the relation * ppilist - ParamPathInfo nodes for parameterized Paths, if any * cheapest_startup_path - the pathlist member with lowest startup cost * (regardless of its ordering; but must be * unparameterized) * cheapest_total_path - the pathlist member with lowest total cost * (regardless of its ordering; but must be * unparameterized) * cheapest_unique_path - for caching cheapest path to produce unique * (no duplicates) output from relation * cheapest_parameterized_paths - paths with cheapest total costs for * their parameterizations; always includes * cheapest_total_path * * If the relation is a base relation it will have these fields set: * * relid - RTE index (this is redundant with the relids field, but * is provided for convenience of access) * rtekind - distinguishes plain relation, subquery, or function RTE * min_attr, max_attr - range of valid AttrNumbers for rel * attr_needed - array of bitmapsets indicating the highest joinrel * in which each attribute is needed; if bit 0 is set then * the attribute is needed as part of final targetlist * attr_widths - cache space for per-attribute width estimates; * zero means not computed yet * indexlist - list of IndexOptInfo nodes for relation's indexes * (always NIL if it's not a table) * pages - number of disk pages in relation (zero if not a table) * tuples - number of tuples in relation (not considering restrictions) * allvisfrac - fraction of disk pages that are marked all-visible * subplan - plan for subquery (NULL if it's not a subquery) * subroot - PlannerInfo for subquery (NULL if it's not a subquery) * fdwroutine - function hooks for FDW, if foreign table (else NULL) * fdw_private - private state for FDW, if foreign table (else NULL) * * Note: for a subquery, tuples, subplan, subroot are not set immediately * upon creation of the RelOptInfo object; they are filled in when * set_subquery_pathlist processes the object. Likewise, fdwroutine * and fdw_private are filled during initial path creation. * * For otherrels that are appendrel members, these fields are filled * in just as for a baserel. * * The presence of the remaining fields depends on the restrictions * and joins that the relation participates in: * * baserestrictinfo - List of RestrictInfo nodes, containing info about * each non-join qualification clause in which this relation * participates (only used for base rels) * baserestrictcost - Estimated cost of evaluating the baserestrictinfo * clauses at a single tuple (only used for base rels) * joininfo - List of RestrictInfo nodes, containing info about each * join clause in which this relation participates (but * note this excludes clauses that might be derivable from * EquivalenceClasses) * has_eclass_joins - flag that EquivalenceClass joins are possible * * Note: Keeping a restrictinfo list in the RelOptInfo is useful only for * base rels, because for a join rel the set of clauses that are treated as * restrict clauses varies depending on which sub-relations we choose to join. * (For example, in a 3-base-rel join, a clause relating rels 1 and 2 must be * treated as a restrictclause if we join {1} and {2 3} to make {1 2 3}; but * if we join {1 2} and {3} then that clause will be a restrictclause in {1 2} * and should not be processed again at the level of {1 2 3}.) Therefore, * the restrictinfo list in the join case appears in individual JoinPaths * (field joinrestrictinfo), not in the parent relation. But it's OK for * the RelOptInfo to store the joininfo list, because that is the same * for a given rel no matter how we form it. * * We store baserestrictcost in the RelOptInfo (for base relations) because * we know we will need it at least once (to price the sequential scan) * and may need it multiple times to price index scans. *---------- */ typedef enum RelOptKind { RELOPT_BASEREL, RELOPT_JOINREL, RELOPT_OTHER_MEMBER_REL, RELOPT_DEADREL } RelOptKind; typedef struct RelOptInfo { NodeTag type; RelOptKind reloptkind; /* all relations included in this RelOptInfo */ Relids relids; /* set of base relids (rangetable indexes) */ /* size estimates generated by planner */ double rows; /* estimated number of result tuples */ int width; /* estimated avg width of result tuples */ /* materialization information */ List *reltargetlist; /* Vars to be output by scan of relation */ List *pathlist; /* Path structures */ List *ppilist; /* ParamPathInfos used in pathlist */ struct Path *cheapest_startup_path; struct Path *cheapest_total_path; struct Path *cheapest_unique_path; List *cheapest_parameterized_paths; /* information about a base rel (not set for join rels!) */ Index relid; Oid reltablespace; /* containing tablespace */ RTEKind rtekind; /* RELATION, SUBQUERY, or FUNCTION */ AttrNumber min_attr; /* smallest attrno of rel (often <0) */ AttrNumber max_attr; /* largest attrno of rel */ Relids *attr_needed; /* array indexed [min_attr .. max_attr] */ int32 *attr_widths; /* array indexed [min_attr .. max_attr] */ List *indexlist; /* list of IndexOptInfo */ BlockNumber pages; /* size estimates derived from pg_class */ double tuples; double allvisfrac; /* use "struct Plan" to avoid including plannodes.h here */ struct Plan *subplan; /* if subquery */ PlannerInfo *subroot; /* if subquery */ /* use "struct FdwRoutine" to avoid including fdwapi.h here */ struct FdwRoutine *fdwroutine; /* if foreign table */ void *fdw_private; /* if foreign table */ /* used by various scans and joins: */ List *baserestrictinfo; /* RestrictInfo structures (if base * rel) */ QualCost baserestrictcost; /* cost of evaluating the above */ List *joininfo; /* RestrictInfo structures for join clauses * involving this rel */ bool has_eclass_joins; /* T means joininfo is incomplete */ } RelOptInfo; /* * IndexOptInfo * Per-index information for planning/optimization * * indexkeys[], indexcollations[], opfamily[], and opcintype[] * each have ncolumns entries. * * sortopfamily[], reverse_sort[], and nulls_first[] likewise have * ncolumns entries, if the index is ordered; but if it is unordered, * those pointers are NULL. * * Zeroes in the indexkeys[] array indicate index columns that are * expressions; there is one element in indexprs for each such column. * * For an ordered index, reverse_sort[] and nulls_first[] describe the * sort ordering of a forward indexscan; we can also consider a backward * indexscan, which will generate the reverse ordering. * * The indexprs and indpred expressions have been run through * prepqual.c and eval_const_expressions() for ease of matching to * WHERE clauses. indpred is in implicit-AND form. * * indextlist is a TargetEntry list representing the index columns. * It provides an equivalent base-relation Var for each simple column, * and links to the matching indexprs element for each expression column. */ typedef struct IndexOptInfo { NodeTag type; Oid indexoid; /* OID of the index relation */ Oid reltablespace; /* tablespace of index (not table) */ RelOptInfo *rel; /* back-link to index's table */ /* statistics from pg_class */ BlockNumber pages; /* number of disk pages in index */ double tuples; /* number of index tuples in index */ /* index descriptor information */ int ncolumns; /* number of columns in index */ int *indexkeys; /* column numbers of index's keys, or 0 */ Oid *indexcollations; /* OIDs of collations of index columns */ Oid *opfamily; /* OIDs of operator families for columns */ Oid *opcintype; /* OIDs of opclass declared input data types */ Oid *sortopfamily; /* OIDs of btree opfamilies, if orderable */ bool *reverse_sort; /* is sort order descending? */ bool *nulls_first; /* do NULLs come first in the sort order? */ Oid relam; /* OID of the access method (in pg_am) */ RegProcedure amcostestimate; /* OID of the access method's cost fcn */ List *indexprs; /* expressions for non-simple index columns */ List *indpred; /* predicate if a partial index, else NIL */ List *indextlist; /* targetlist representing index columns */ bool predOK; /* true if predicate matches query */ bool unique; /* true if a unique index */ bool immediate; /* is uniqueness enforced immediately? */ bool hypothetical; /* true if index doesn't really exist */ bool canreturn; /* can index return IndexTuples? */ bool amcanorderbyop; /* does AM support order by operator result? */ bool amoptionalkey; /* can query omit key for the first column? */ bool amsearcharray; /* can AM handle ScalarArrayOpExpr quals? */ bool amsearchnulls; /* can AM search for NULL/NOT NULL entries? */ bool amhasgettuple; /* does AM have amgettuple interface? */ bool amhasgetbitmap; /* does AM have amgetbitmap interface? */ } IndexOptInfo; /* * EquivalenceClasses * * Whenever we can determine that a mergejoinable equality clause A = B is * not delayed by any outer join, we create an EquivalenceClass containing * the expressions A and B to record this knowledge. If we later find another * equivalence B = C, we add C to the existing EquivalenceClass; this may * require merging two existing EquivalenceClasses. At the end of the qual * distribution process, we have sets of values that are known all transitively * equal to each other, where "equal" is according to the rules of the btree * operator family(s) shown in ec_opfamilies, as well as the collation shown * by ec_collation. (We restrict an EC to contain only equalities whose * operators belong to the same set of opfamilies. This could probably be * relaxed, but for now it's not worth the trouble, since nearly all equality * operators belong to only one btree opclass anyway. Similarly, we suppose * that all or none of the input datatypes are collatable, so that a single * collation value is sufficient.) * * We also use EquivalenceClasses as the base structure for PathKeys, letting * us represent knowledge about different sort orderings being equivalent. * Since every PathKey must reference an EquivalenceClass, we will end up * with single-member EquivalenceClasses whenever a sort key expression has * not been equivalenced to anything else. It is also possible that such an * EquivalenceClass will contain a volatile expression ("ORDER BY random()"), * which is a case that can't arise otherwise since clauses containing * volatile functions are never considered mergejoinable. We mark such * EquivalenceClasses specially to prevent them from being merged with * ordinary EquivalenceClasses. Also, for volatile expressions we have * to be careful to match the EquivalenceClass to the correct targetlist * entry: consider SELECT random() AS a, random() AS b ... ORDER BY b,a. * So we record the SortGroupRef of the originating sort clause. * * We allow equality clauses appearing below the nullable side of an outer join * to form EquivalenceClasses, but these have a slightly different meaning: * the included values might be all NULL rather than all the same non-null * values. See src/backend/optimizer/README for more on that point. * * NB: if ec_merged isn't NULL, this class has been merged into another, and * should be ignored in favor of using the pointed-to class. */ typedef struct EquivalenceClass { NodeTag type; List *ec_opfamilies; /* btree operator family OIDs */ Oid ec_collation; /* collation, if datatypes are collatable */ List *ec_members; /* list of EquivalenceMembers */ List *ec_sources; /* list of generating RestrictInfos */ List *ec_derives; /* list of derived RestrictInfos */ Relids ec_relids; /* all relids appearing in ec_members */ bool ec_has_const; /* any pseudoconstants in ec_members? */ bool ec_has_volatile; /* the (sole) member is a volatile expr */ bool ec_below_outer_join; /* equivalence applies below an OJ */ bool ec_broken; /* failed to generate needed clauses? */ Index ec_sortref; /* originating sortclause label, or 0 */ struct EquivalenceClass *ec_merged; /* set if merged into another EC */ } EquivalenceClass; /* * If an EC contains a const and isn't below-outer-join, any PathKey depending * on it must be redundant, since there's only one possible value of the key. */ #define EC_MUST_BE_REDUNDANT(eclass) \ ((eclass)->ec_has_const && !(eclass)->ec_below_outer_join) /* * EquivalenceMember - one member expression of an EquivalenceClass * * em_is_child signifies that this element was built by transposing a member * for an appendrel parent relation to represent the corresponding expression * for an appendrel child. These members are used for determining the * pathkeys of scans on the child relation and for explicitly sorting the * child when necessary to build a MergeAppend path for the whole appendrel * tree. An em_is_child member has no impact on the properties of the EC as a * whole; in particular the EC's ec_relids field does NOT include the child * relation. An em_is_child member should never be marked em_is_const nor * cause ec_has_const or ec_has_volatile to be set, either. Thus, em_is_child * members are not really full-fledged members of the EC, but just reflections * or doppelgangers of real members. Most operations on EquivalenceClasses * should ignore em_is_child members, and those that don't should test * em_relids to make sure they only consider relevant members. * * em_datatype is usually the same as exprType(em_expr), but can be * different when dealing with a binary-compatible opfamily; in particular * anyarray_ops would never work without this. Use em_datatype when * looking up a specific btree operator to work with this expression. */ typedef struct EquivalenceMember { NodeTag type; Expr *em_expr; /* the expression represented */ Relids em_relids; /* all relids appearing in em_expr */ Relids em_nullable_relids; /* nullable by lower outer joins */ bool em_is_const; /* expression is pseudoconstant? */ bool em_is_child; /* derived version for a child relation? */ Oid em_datatype; /* the "nominal type" used by the opfamily */ } EquivalenceMember; /* * PathKeys * * The sort ordering of a path is represented by a list of PathKey nodes. * An empty list implies no known ordering. Otherwise the first item * represents the primary sort key, the second the first secondary sort key, * etc. The value being sorted is represented by linking to an * EquivalenceClass containing that value and including pk_opfamily among its * ec_opfamilies. The EquivalenceClass tells which collation to use, too. * This is a convenient method because it makes it trivial to detect * equivalent and closely-related orderings. (See optimizer/README for more * information.) * * Note: pk_strategy is either BTLessStrategyNumber (for ASC) or * BTGreaterStrategyNumber (for DESC). We assume that all ordering-capable * index types will use btree-compatible strategy numbers. */ typedef struct PathKey { NodeTag type; EquivalenceClass *pk_eclass; /* the value that is ordered */ Oid pk_opfamily; /* btree opfamily defining the ordering */ int pk_strategy; /* sort direction (ASC or DESC) */ bool pk_nulls_first; /* do NULLs come before normal values? */ } PathKey; /* * ParamPathInfo * * All parameterized paths for a given relation with given required outer rels * link to a single ParamPathInfo, which stores common information such as * the estimated rowcount for this parameterization. We do this partly to * avoid recalculations, but mostly to ensure that the estimated rowcount * is in fact the same for every such path. * * Note: ppi_clauses is only used in ParamPathInfos for base relation paths; * in join cases it's NIL because the set of relevant clauses varies depending * on how the join is formed. The relevant clauses will appear in each * parameterized join path's joinrestrictinfo list, instead. */ typedef struct ParamPathInfo { NodeTag type; Relids ppi_req_outer; /* rels supplying parameters used by path */ double ppi_rows; /* estimated number of result tuples */ List *ppi_clauses; /* join clauses available from outer rels */ } ParamPathInfo; /* * Type "Path" is used as-is for sequential-scan paths, as well as some other * simple plan types that we don't need any extra information in the path for. * For other path types it is the first component of a larger struct. * * "pathtype" is the NodeTag of the Plan node we could build from this Path. * It is partially redundant with the Path's NodeTag, but allows us to use * the same Path type for multiple Plan types when there is no need to * distinguish the Plan type during path processing. * * "param_info", if not NULL, links to a ParamPathInfo that identifies outer * relation(s) that provide parameter values to each scan of this path. * That means this path can only be joined to those rels by means of nestloop * joins with this path on the inside. Also note that a parameterized path * is responsible for testing all "movable" joinclauses involving this rel * and the specified outer rel(s). * * "rows" is the same as parent->rows in simple paths, but in parameterized * paths and UniquePaths it can be less than parent->rows, reflecting the * fact that we've filtered by extra join conditions or removed duplicates. * * "pathkeys" is a List of PathKey nodes (see above), describing the sort * ordering of the path's output rows. */ typedef struct Path { NodeTag type; NodeTag pathtype; /* tag identifying scan/join method */ RelOptInfo *parent; /* the relation this path can build */ ParamPathInfo *param_info; /* parameterization info, or NULL if none */ /* estimated size/costs for path (see costsize.c for more info) */ double rows; /* estimated number of result tuples */ Cost startup_cost; /* cost expended before fetching any tuples */ Cost total_cost; /* total cost (assuming all tuples fetched) */ List *pathkeys; /* sort ordering of path's output */ /* pathkeys is a List of PathKey nodes; see above */ } Path; /* Macro for extracting a path's parameterization relids; beware double eval */ #define PATH_REQ_OUTER(path) \ ((path)->param_info ? (path)->param_info->ppi_req_outer : (Relids) NULL) /*---------- * IndexPath represents an index scan over a single index. * * This struct is used for both regular indexscans and index-only scans; * path.pathtype is T_IndexScan or T_IndexOnlyScan to show which is meant. * * 'indexinfo' is the index to be scanned. * * 'indexclauses' is a list of index qualification clauses, with implicit * AND semantics across the list. Each clause is a RestrictInfo node from * the query's WHERE or JOIN conditions. An empty list implies a full * index scan. * * 'indexquals' has the same structure as 'indexclauses', but it contains * the actual index qual conditions that can be used with the index. * In simple cases this is identical to 'indexclauses', but when special * indexable operators appear in 'indexclauses', they are replaced by the * derived indexscannable conditions in 'indexquals'. * * 'indexqualcols' is an integer list of index column numbers (zero-based) * of the same length as 'indexquals', showing which index column each qual * is meant to be used with. 'indexquals' is required to be ordered by * index column, so 'indexqualcols' must form a nondecreasing sequence. * (The order of multiple quals for the same index column is unspecified.) * * 'indexorderbys', if not NIL, is a list of ORDER BY expressions that have * been found to be usable as ordering operators for an amcanorderbyop index. * The list must match the path's pathkeys, ie, one expression per pathkey * in the same order. These are not RestrictInfos, just bare expressions, * since they generally won't yield booleans. Also, unlike the case for * quals, it's guaranteed that each expression has the index key on the left * side of the operator. * * 'indexorderbycols' is an integer list of index column numbers (zero-based) * of the same length as 'indexorderbys', showing which index column each * ORDER BY expression is meant to be used with. (There is no restriction * on which index column each ORDER BY can be used with.) * * 'indexscandir' is one of: * ForwardScanDirection: forward scan of an ordered index * BackwardScanDirection: backward scan of an ordered index * NoMovementScanDirection: scan of an unordered index, or don't care * (The executor doesn't care whether it gets ForwardScanDirection or * NoMovementScanDirection for an indexscan, but the planner wants to * distinguish ordered from unordered indexes for building pathkeys.) * * 'indextotalcost' and 'indexselectivity' are saved in the IndexPath so that * we need not recompute them when considering using the same index in a * bitmap index/heap scan (see BitmapHeapPath). The costs of the IndexPath * itself represent the costs of an IndexScan or IndexOnlyScan plan type. *---------- */ typedef struct IndexPath { Path path; IndexOptInfo *indexinfo; List *indexclauses; List *indexquals; List *indexqualcols; List *indexorderbys; List *indexorderbycols; ScanDirection indexscandir; Cost indextotalcost; Selectivity indexselectivity; } IndexPath; /* * BitmapHeapPath represents one or more indexscans that generate TID bitmaps * instead of directly accessing the heap, followed by AND/OR combinations * to produce a single bitmap, followed by a heap scan that uses the bitmap. * Note that the output is always considered unordered, since it will come * out in physical heap order no matter what the underlying indexes did. * * The individual indexscans are represented by IndexPath nodes, and any * logic on top of them is represented by a tree of BitmapAndPath and * BitmapOrPath nodes. Notice that we can use the same IndexPath node both * to represent a regular (or index-only) index scan plan, and as the child * of a BitmapHeapPath that represents scanning the same index using a * BitmapIndexScan. The startup_cost and total_cost figures of an IndexPath * always represent the costs to use it as a regular (or index-only) * IndexScan. The costs of a BitmapIndexScan can be computed using the * IndexPath's indextotalcost and indexselectivity. */ typedef struct BitmapHeapPath { Path path; Path *bitmapqual; /* IndexPath, BitmapAndPath, BitmapOrPath */ } BitmapHeapPath; /* * BitmapAndPath represents a BitmapAnd plan node; it can only appear as * part of the substructure of a BitmapHeapPath. The Path structure is * a bit more heavyweight than we really need for this, but for simplicity * we make it a derivative of Path anyway. */ typedef struct BitmapAndPath { Path path; List *bitmapquals; /* IndexPaths and BitmapOrPaths */ Selectivity bitmapselectivity; } BitmapAndPath; /* * BitmapOrPath represents a BitmapOr plan node; it can only appear as * part of the substructure of a BitmapHeapPath. The Path structure is * a bit more heavyweight than we really need for this, but for simplicity * we make it a derivative of Path anyway. */ typedef struct BitmapOrPath { Path path; List *bitmapquals; /* IndexPaths and BitmapAndPaths */ Selectivity bitmapselectivity; } BitmapOrPath; /* * TidPath represents a scan by TID * * tidquals is an implicitly OR'ed list of qual expressions of the form * "CTID = pseudoconstant" or "CTID = ANY(pseudoconstant_array)". * Note they are bare expressions, not RestrictInfos. */ typedef struct TidPath { Path path; List *tidquals; /* qual(s) involving CTID = something */ } TidPath; /* * ForeignPath represents a potential scan of a foreign table * * fdw_private stores FDW private data about the scan. While fdw_private is * not actually touched by the core code during normal operations, it's * generally a good idea to use a representation that can be dumped by * nodeToString(), so that you can examine the structure during debugging * with tools like pprint(). */ typedef struct ForeignPath { Path path; List *fdw_private; } ForeignPath; /* * AppendPath represents an Append plan, ie, successive execution of * several member plans. * * Note: it is possible for "subpaths" to contain only one, or even no, * elements. These cases are optimized during create_append_plan. * In particular, an AppendPath with no subpaths is a "dummy" path that * is created to represent the case that a relation is provably empty. */ typedef struct AppendPath { Path path; List *subpaths; /* list of component Paths */ } AppendPath; #define IS_DUMMY_PATH(p) \ (IsA((p), AppendPath) && ((AppendPath *) (p))->subpaths == NIL) /* A relation that's been proven empty will have one path that is dummy */ #define IS_DUMMY_REL(r) \ ((r)->cheapest_total_path != NULL && \ IS_DUMMY_PATH((r)->cheapest_total_path)) /* * MergeAppendPath represents a MergeAppend plan, ie, the merging of sorted * results from several member plans to produce similarly-sorted output. */ typedef struct MergeAppendPath { Path path; List *subpaths; /* list of component Paths */ double limit_tuples; /* hard limit on output tuples, or -1 */ } MergeAppendPath; /* * ResultPath represents use of a Result plan node to compute a variable-free * targetlist with no underlying tables (a "SELECT expressions" query). * The query could have a WHERE clause, too, represented by "quals". * * Note that quals is a list of bare clauses, not RestrictInfos. */ typedef struct ResultPath { Path path; List *quals; } ResultPath; /* * MaterialPath represents use of a Material plan node, i.e., caching of * the output of its subpath. This is used when the subpath is expensive * and needs to be scanned repeatedly, or when we need mark/restore ability * and the subpath doesn't have it. */ typedef struct MaterialPath { Path path; Path *subpath; } MaterialPath; /* * UniquePath represents elimination of distinct rows from the output of * its subpath. * * This is unlike the other Path nodes in that it can actually generate * different plans: either hash-based or sort-based implementation, or a * no-op if the input path can be proven distinct already. The decision * is sufficiently localized that it's not worth having separate Path node * types. (Note: in the no-op case, we could eliminate the UniquePath node * entirely and just return the subpath; but it's convenient to have a * UniquePath in the path tree to signal upper-level routines that the input * is known distinct.) */ typedef enum { UNIQUE_PATH_NOOP, /* input is known unique already */ UNIQUE_PATH_HASH, /* use hashing */ UNIQUE_PATH_SORT /* use sorting */ } UniquePathMethod; typedef struct UniquePath { Path path; Path *subpath; UniquePathMethod umethod; List *in_operators; /* equality operators of the IN clause */ List *uniq_exprs; /* expressions to be made unique */ } UniquePath; /* * All join-type paths share these fields. */ typedef struct JoinPath { Path path; JoinType jointype; Path *outerjoinpath; /* path for the outer side of the join */ Path *innerjoinpath; /* path for the inner side of the join */ List *joinrestrictinfo; /* RestrictInfos to apply to join */ /* * See the notes for RelOptInfo and ParamPathInfo to understand why * joinrestrictinfo is needed in JoinPath, and can't be merged into the * parent RelOptInfo. */ } JoinPath; /* * A nested-loop path needs no special fields. */ typedef JoinPath NestPath; /* * A mergejoin path has these fields. * * Unlike other path types, a MergePath node doesn't represent just a single * run-time plan node: it can represent up to four. Aside from the MergeJoin * node itself, there can be a Sort node for the outer input, a Sort node * for the inner input, and/or a Material node for the inner input. We could * represent these nodes by separate path nodes, but considering how many * different merge paths are investigated during a complex join problem, * it seems better to avoid unnecessary palloc overhead. * * path_mergeclauses lists the clauses (in the form of RestrictInfos) * that will be used in the merge. * * Note that the mergeclauses are a subset of the parent relation's * restriction-clause list. Any join clauses that are not mergejoinable * appear only in the parent's restrict list, and must be checked by a * qpqual at execution time. * * outersortkeys (resp. innersortkeys) is NIL if the outer path * (resp. inner path) is already ordered appropriately for the * mergejoin. If it is not NIL then it is a PathKeys list describing * the ordering that must be created by an explicit Sort node. * * materialize_inner is TRUE if a Material node should be placed atop the * inner input. This may appear with or without an inner Sort step. */ typedef struct MergePath { JoinPath jpath; List *path_mergeclauses; /* join clauses to be used for merge */ List *outersortkeys; /* keys for explicit sort, if any */ List *innersortkeys; /* keys for explicit sort, if any */ bool materialize_inner; /* add Materialize to inner? */ } MergePath; /* * A hashjoin path has these fields. * * The remarks above for mergeclauses apply for hashclauses as well. * * Hashjoin does not care what order its inputs appear in, so we have * no need for sortkeys. */ typedef struct HashPath { JoinPath jpath; List *path_hashclauses; /* join clauses used for hashing */ int num_batches; /* number of batches expected */ } HashPath; /* * Restriction clause info. * * We create one of these for each AND sub-clause of a restriction condition * (WHERE or JOIN/ON clause). Since the restriction clauses are logically * ANDed, we can use any one of them or any subset of them to filter out * tuples, without having to evaluate the rest. The RestrictInfo node itself * stores data used by the optimizer while choosing the best query plan. * * If a restriction clause references a single base relation, it will appear * in the baserestrictinfo list of the RelOptInfo for that base rel. * * If a restriction clause references more than one base rel, it will * appear in the joininfo list of every RelOptInfo that describes a strict * subset of the base rels mentioned in the clause. The joininfo lists are * used to drive join tree building by selecting plausible join candidates. * The clause cannot actually be applied until we have built a join rel * containing all the base rels it references, however. * * When we construct a join rel that includes all the base rels referenced * in a multi-relation restriction clause, we place that clause into the * joinrestrictinfo lists of paths for the join rel, if neither left nor * right sub-path includes all base rels referenced in the clause. The clause * will be applied at that join level, and will not propagate any further up * the join tree. (Note: the "predicate migration" code was once intended to * push restriction clauses up and down the plan tree based on evaluation * costs, but it's dead code and is unlikely to be resurrected in the * foreseeable future.) * * Note that in the presence of more than two rels, a multi-rel restriction * might reach different heights in the join tree depending on the join * sequence we use. So, these clauses cannot be associated directly with * the join RelOptInfo, but must be kept track of on a per-join-path basis. * * RestrictInfos that represent equivalence conditions (i.e., mergejoinable * equalities that are not outerjoin-delayed) are handled a bit differently. * Initially we attach them to the EquivalenceClasses that are derived from * them. When we construct a scan or join path, we look through all the * EquivalenceClasses and generate derived RestrictInfos representing the * minimal set of conditions that need to be checked for this particular scan * or join to enforce that all members of each EquivalenceClass are in fact * equal in all rows emitted by the scan or join. * * When dealing with outer joins we have to be very careful about pushing qual * clauses up and down the tree. An outer join's own JOIN/ON conditions must * be evaluated exactly at that join node, unless they are "degenerate" * conditions that reference only Vars from the nullable side of the join. * Quals appearing in WHERE or in a JOIN above the outer join cannot be pushed * down below the outer join, if they reference any nullable Vars. * RestrictInfo nodes contain a flag to indicate whether a qual has been * pushed down to a lower level than its original syntactic placement in the * join tree would suggest. If an outer join prevents us from pushing a qual * down to its "natural" semantic level (the level associated with just the * base rels used in the qual) then we mark the qual with a "required_relids" * value including more than just the base rels it actually uses. By * pretending that the qual references all the rels required to form the outer * join, we prevent it from being evaluated below the outer join's joinrel. * When we do form the outer join's joinrel, we still need to distinguish * those quals that are actually in that join's JOIN/ON condition from those * that appeared elsewhere in the tree and were pushed down to the join rel * because they used no other rels. That's what the is_pushed_down flag is * for; it tells us that a qual is not an OUTER JOIN qual for the set of base * rels listed in required_relids. A clause that originally came from WHERE * or an INNER JOIN condition will *always* have its is_pushed_down flag set. * It's possible for an OUTER JOIN clause to be marked is_pushed_down too, * if we decide that it can be pushed down into the nullable side of the join. * In that case it acts as a plain filter qual for wherever it gets evaluated. * (In short, is_pushed_down is only false for non-degenerate outer join * conditions. Possibly we should rename it to reflect that meaning?) * * RestrictInfo nodes also contain an outerjoin_delayed flag, which is true * if the clause's applicability must be delayed due to any outer joins * appearing below it (ie, it has to be postponed to some join level higher * than the set of relations it actually references). * * There is also an outer_relids field, which is NULL except for outer join * clauses; for those, it is the set of relids on the outer side of the * clause's outer join. (These are rels that the clause cannot be applied to * in parameterized scans, since pushing it into the join's outer side would * lead to wrong answers.) * * There is also a nullable_relids field, which is the set of rels the clause * references that can be forced null by some outer join below the clause. * * outerjoin_delayed = true is subtly different from nullable_relids != NULL: * a clause might reference some nullable rels and yet not be * outerjoin_delayed because it also references all the other rels of the * outer join(s). A clause that is not outerjoin_delayed can be enforced * anywhere it is computable. * * In general, the referenced clause might be arbitrarily complex. The * kinds of clauses we can handle as indexscan quals, mergejoin clauses, * or hashjoin clauses are limited (e.g., no volatile functions). The code * for each kind of path is responsible for identifying the restrict clauses * it can use and ignoring the rest. Clauses not implemented by an indexscan, * mergejoin, or hashjoin will be placed in the plan qual or joinqual field * of the finished Plan node, where they will be enforced by general-purpose * qual-expression-evaluation code. (But we are still entitled to count * their selectivity when estimating the result tuple count, if we * can guess what it is...) * * When the referenced clause is an OR clause, we generate a modified copy * in which additional RestrictInfo nodes are inserted below the top-level * OR/AND structure. This is a convenience for OR indexscan processing: * indexquals taken from either the top level or an OR subclause will have * associated RestrictInfo nodes. * * The can_join flag is set true if the clause looks potentially useful as * a merge or hash join clause, that is if it is a binary opclause with * nonoverlapping sets of relids referenced in the left and right sides. * (Whether the operator is actually merge or hash joinable isn't checked, * however.) * * The pseudoconstant flag is set true if the clause contains no Vars of * the current query level and no volatile functions. Such a clause can be * pulled out and used as a one-time qual in a gating Result node. We keep * pseudoconstant clauses in the same lists as other RestrictInfos so that * the regular clause-pushing machinery can assign them to the correct join * level, but they need to be treated specially for cost and selectivity * estimates. Note that a pseudoconstant clause can never be an indexqual * or merge or hash join clause, so it's of no interest to large parts of * the planner. * * When join clauses are generated from EquivalenceClasses, there may be * several equally valid ways to enforce join equivalence, of which we need * apply only one. We mark clauses of this kind by setting parent_ec to * point to the generating EquivalenceClass. Multiple clauses with the same * parent_ec in the same join are redundant. */ typedef struct RestrictInfo { NodeTag type; Expr *clause; /* the represented clause of WHERE or JOIN */ bool is_pushed_down; /* TRUE if clause was pushed down in level */ bool outerjoin_delayed; /* TRUE if delayed by lower outer join */ bool can_join; /* see comment above */ bool pseudoconstant; /* see comment above */ /* The set of relids (varnos) actually referenced in the clause: */ Relids clause_relids; /* The set of relids required to evaluate the clause: */ Relids required_relids; /* If an outer-join clause, the outer-side relations, else NULL: */ Relids outer_relids; /* The relids used in the clause that are nullable by lower outer joins: */ Relids nullable_relids; /* These fields are set for any binary opclause: */ Relids left_relids; /* relids in left side of clause */ Relids right_relids; /* relids in right side of clause */ /* This field is NULL unless clause is an OR clause: */ Expr *orclause; /* modified clause with RestrictInfos */ /* This field is NULL unless clause is potentially redundant: */ EquivalenceClass *parent_ec; /* generating EquivalenceClass */ /* cache space for cost and selectivity */ QualCost eval_cost; /* eval cost of clause; -1 if not yet set */ Selectivity norm_selec; /* selectivity for "normal" (JOIN_INNER) * semantics; -1 if not yet set; >1 means a * redundant clause */ Selectivity outer_selec; /* selectivity for outer join semantics; -1 if * not yet set */ /* valid if clause is mergejoinable, else NIL */ List *mergeopfamilies; /* opfamilies containing clause operator */ /* cache space for mergeclause processing; NULL if not yet set */ EquivalenceClass *left_ec; /* EquivalenceClass containing lefthand */ EquivalenceClass *right_ec; /* EquivalenceClass containing righthand */ EquivalenceMember *left_em; /* EquivalenceMember for lefthand */ EquivalenceMember *right_em; /* EquivalenceMember for righthand */ List *scansel_cache; /* list of MergeScanSelCache structs */ /* transient workspace for use while considering a specific join path */ bool outer_is_left; /* T = outer var on left, F = on right */ /* valid if clause is hashjoinable, else InvalidOid: */ Oid hashjoinoperator; /* copy of clause operator */ /* cache space for hashclause processing; -1 if not yet set */ Selectivity left_bucketsize; /* avg bucketsize of left side */ Selectivity right_bucketsize; /* avg bucketsize of right side */ } RestrictInfo; /* * Since mergejoinscansel() is a relatively expensive function, and would * otherwise be invoked many times while planning a large join tree, * we go out of our way to cache its results. Each mergejoinable * RestrictInfo carries a list of the specific sort orderings that have * been considered for use with it, and the resulting selectivities. */ typedef struct MergeScanSelCache { /* Ordering details (cache lookup key) */ Oid opfamily; /* btree opfamily defining the ordering */ Oid collation; /* collation for the ordering */ int strategy; /* sort direction (ASC or DESC) */ bool nulls_first; /* do NULLs come before normal values? */ /* Results */ Selectivity leftstartsel; /* first-join fraction for clause left side */ Selectivity leftendsel; /* last-join fraction for clause left side */ Selectivity rightstartsel; /* first-join fraction for clause right side */ Selectivity rightendsel; /* last-join fraction for clause right side */ } MergeScanSelCache; /* * Placeholder node for an expression to be evaluated below the top level * of a plan tree. This is used during planning to represent the contained * expression. At the end of the planning process it is replaced by either * the contained expression or a Var referring to a lower-level evaluation of * the contained expression. Typically the evaluation occurs below an outer * join, and Var references above the outer join might thereby yield NULL * instead of the expression value. * * Although the planner treats this as an expression node type, it is not * recognized by the parser or executor, so we declare it here rather than * in primnodes.h. */ typedef struct PlaceHolderVar { Expr xpr; Expr *phexpr; /* the represented expression */ Relids phrels; /* base relids syntactically within expr src */ Index phid; /* ID for PHV (unique within planner run) */ Index phlevelsup; /* > 0 if PHV belongs to outer query */ } PlaceHolderVar; /* * "Special join" info. * * One-sided outer joins constrain the order of joining partially but not * completely. We flatten such joins into the planner's top-level list of * relations to join, but record information about each outer join in a * SpecialJoinInfo struct. These structs are kept in the PlannerInfo node's * join_info_list. * * Similarly, semijoins and antijoins created by flattening IN (subselect) * and EXISTS(subselect) clauses create partial constraints on join order. * These are likewise recorded in SpecialJoinInfo structs. * * We make SpecialJoinInfos for FULL JOINs even though there is no flexibility * of planning for them, because this simplifies make_join_rel()'s API. * * min_lefthand and min_righthand are the sets of base relids that must be * available on each side when performing the special join. lhs_strict is * true if the special join's condition cannot succeed when the LHS variables * are all NULL (this means that an outer join can commute with upper-level * outer joins even if it appears in their RHS). We don't bother to set * lhs_strict for FULL JOINs, however. * * It is not valid for either min_lefthand or min_righthand to be empty sets; * if they were, this would break the logic that enforces join order. * * syn_lefthand and syn_righthand are the sets of base relids that are * syntactically below this special join. (These are needed to help compute * min_lefthand and min_righthand for higher joins.) * * delay_upper_joins is set TRUE if we detect a pushed-down clause that has * to be evaluated after this join is formed (because it references the RHS). * Any outer joins that have such a clause and this join in their RHS cannot * commute with this join, because that would leave noplace to check the * pushed-down clause. (We don't track this for FULL JOINs, either.) * * join_quals is an implicit-AND list of the quals syntactically associated * with the join (they may or may not end up being applied at the join level). * This is just a side list and does not drive actual application of quals. * For JOIN_SEMI joins, this is cleared to NIL in create_unique_path() if * the join is found not to be suitable for a uniqueify-the-RHS plan. * * jointype is never JOIN_RIGHT; a RIGHT JOIN is handled by switching * the inputs to make it a LEFT JOIN. So the allowed values of jointype * in a join_info_list member are only LEFT, FULL, SEMI, or ANTI. * * For purposes of join selectivity estimation, we create transient * SpecialJoinInfo structures for regular inner joins; so it is possible * to have jointype == JOIN_INNER in such a structure, even though this is * not allowed within join_info_list. We also create transient * SpecialJoinInfos with jointype == JOIN_INNER for outer joins, since for * cost estimation purposes it is sometimes useful to know the join size under * plain innerjoin semantics. Note that lhs_strict, delay_upper_joins, and * join_quals are not set meaningfully within such structs. */ typedef struct SpecialJoinInfo { NodeTag type; Relids min_lefthand; /* base relids in minimum LHS for join */ Relids min_righthand; /* base relids in minimum RHS for join */ Relids syn_lefthand; /* base relids syntactically within LHS */ Relids syn_righthand; /* base relids syntactically within RHS */ JoinType jointype; /* always INNER, LEFT, FULL, SEMI, or ANTI */ bool lhs_strict; /* joinclause is strict for some LHS rel */ bool delay_upper_joins; /* can't commute with upper RHS */ List *join_quals; /* join quals, in implicit-AND list format */ } SpecialJoinInfo; /* * Append-relation info. * * When we expand an inheritable table or a UNION-ALL subselect into an * "append relation" (essentially, a list of child RTEs), we build an * AppendRelInfo for each child RTE. The list of AppendRelInfos indicates * which child RTEs must be included when expanding the parent, and each * node carries information needed to translate Vars referencing the parent * into Vars referencing that child. * * These structs are kept in the PlannerInfo node's append_rel_list. * Note that we just throw all the structs into one list, and scan the * whole list when desiring to expand any one parent. We could have used * a more complex data structure (eg, one list per parent), but this would * be harder to update during operations such as pulling up subqueries, * and not really any easier to scan. Considering that typical queries * will not have many different append parents, it doesn't seem worthwhile * to complicate things. * * Note: after completion of the planner prep phase, any given RTE is an * append parent having entries in append_rel_list if and only if its * "inh" flag is set. We clear "inh" for plain tables that turn out not * to have inheritance children, and (in an abuse of the original meaning * of the flag) we set "inh" for subquery RTEs that turn out to be * flattenable UNION ALL queries. This lets us avoid useless searches * of append_rel_list. * * Note: the data structure assumes that append-rel members are single * baserels. This is OK for inheritance, but it prevents us from pulling * up a UNION ALL member subquery if it contains a join. While that could * be fixed with a more complex data structure, at present there's not much * point because no improvement in the plan could result. */ typedef struct AppendRelInfo { NodeTag type; /* * These fields uniquely identify this append relationship. There can be * (in fact, always should be) multiple AppendRelInfos for the same * parent_relid, but never more than one per child_relid, since a given * RTE cannot be a child of more than one append parent. */ Index parent_relid; /* RT index of append parent rel */ Index child_relid; /* RT index of append child rel */ /* * For an inheritance appendrel, the parent and child are both regular * relations, and we store their rowtype OIDs here for use in translating * whole-row Vars. For a UNION-ALL appendrel, the parent and child are * both subqueries with no named rowtype, and we store InvalidOid here. */ Oid parent_reltype; /* OID of parent's composite type */ Oid child_reltype; /* OID of child's composite type */ /* * The N'th element of this list is a Var or expression representing the * child column corresponding to the N'th column of the parent. This is * used to translate Vars referencing the parent rel into references to * the child. A list element is NULL if it corresponds to a dropped * column of the parent (this is only possible for inheritance cases, not * UNION ALL). The list elements are always simple Vars for inheritance * cases, but can be arbitrary expressions in UNION ALL cases. * * Notice we only store entries for user columns (attno > 0). Whole-row * Vars are special-cased, and system columns (attno < 0) need no special * translation since their attnos are the same for all tables. * * Caution: the Vars have varlevelsup = 0. Be careful to adjust as needed * when copying into a subquery. */ List *translated_vars; /* Expressions in the child's Vars */ /* * We store the parent table's OID here for inheritance, or InvalidOid for * UNION ALL. This is only needed to help in generating error messages if * an attempt is made to reference a dropped parent column. */ Oid parent_reloid; /* OID of parent relation */ } AppendRelInfo; /* * For each distinct placeholder expression generated during planning, we * store a PlaceHolderInfo node in the PlannerInfo node's placeholder_list. * This stores info that is needed centrally rather than in each copy of the * PlaceHolderVar. The phid fields identify which PlaceHolderInfo goes with * each PlaceHolderVar. Note that phid is unique throughout a planner run, * not just within a query level --- this is so that we need not reassign ID's * when pulling a subquery into its parent. * * The idea is to evaluate the expression at (only) the ph_eval_at join level, * then allow it to bubble up like a Var until the ph_needed join level. * ph_needed has the same definition as attr_needed for a regular Var. * * ph_may_need is an initial estimate of ph_needed, formed using the * syntactic locations of references to the PHV. We need this in order to * determine whether the PHV reference forces a join ordering constraint: * if the PHV has to be evaluated below the nullable side of an outer join, * and then used above that outer join, we must constrain join order to ensure * there's a valid place to evaluate the PHV below the join. The final * actual ph_needed level might be lower than ph_may_need, but we can't * determine that until later on. Fortunately this doesn't matter for what * we need ph_may_need for: if there's a PHV reference syntactically * above the outer join, it's not going to be allowed to drop below the outer * join, so we would come to the same conclusions about join order even if * we had the final ph_needed value to compare to. * * We create a PlaceHolderInfo only after determining that the PlaceHolderVar * is actually referenced in the plan tree, so that unreferenced placeholders * don't result in unnecessary constraints on join order. */ typedef struct PlaceHolderInfo { NodeTag type; Index phid; /* ID for PH (unique within planner run) */ PlaceHolderVar *ph_var; /* copy of PlaceHolderVar tree */ Relids ph_eval_at; /* lowest level we can evaluate value at */ Relids ph_needed; /* highest level the value is needed at */ Relids ph_may_need; /* highest level it might be needed at */ int32 ph_width; /* estimated attribute width */ } PlaceHolderInfo; /* * For each potentially index-optimizable MIN/MAX aggregate function, * root->minmax_aggs stores a MinMaxAggInfo describing it. */ typedef struct MinMaxAggInfo { NodeTag type; Oid aggfnoid; /* pg_proc Oid of the aggregate */ Oid aggsortop; /* Oid of its sort operator */ Expr *target; /* expression we are aggregating on */ PlannerInfo *subroot; /* modified "root" for planning the subquery */ Path *path; /* access path for subquery */ Cost pathcost; /* estimated cost to fetch first row */ Param *param; /* param for subplan's output */ } MinMaxAggInfo; /* * At runtime, PARAM_EXEC slots are used to pass values around from one plan * node to another. They can be used to pass values down into subqueries (for * outer references in subqueries), or up out of subqueries (for the results * of a subplan), or from a NestLoop plan node into its inner relation (when * the inner scan is parameterized with values from the outer relation). * The planner is responsible for assigning nonconflicting PARAM_EXEC IDs to * the PARAM_EXEC Params it generates. * * Outer references are managed via root->plan_params, which is a list of * PlannerParamItems. While planning a subquery, each parent query level's * plan_params contains the values required from it by the current subquery. * During create_plan(), we use plan_params to track values that must be * passed from outer to inner sides of NestLoop plan nodes. * * The item a PlannerParamItem represents can be one of three kinds: * * A Var: the slot represents a variable of this level that must be passed * down because subqueries have outer references to it, or must be passed * from a NestLoop node to its inner scan. The varlevelsup value in the Var * will always be zero. * * A PlaceHolderVar: this works much like the Var case, except that the * entry is a PlaceHolderVar node with a contained expression. The PHV * will have phlevelsup = 0, and the contained expression is adjusted * to match in level. * * An Aggref (with an expression tree representing its argument): the slot * represents an aggregate expression that is an outer reference for some * subquery. The Aggref itself has agglevelsup = 0, and its argument tree * is adjusted to match in level. * * Note: we detect duplicate Var and PlaceHolderVar parameters and coalesce * them into one slot, but we do not bother to do that for Aggrefs. * The scope of duplicate-elimination only extends across the set of * parameters passed from one query level into a single subquery, or for * nestloop parameters across the set of nestloop parameters used in a single * query level. So there is no possibility of a PARAM_EXEC slot being used * for conflicting purposes. * * In addition, PARAM_EXEC slots are assigned for Params representing outputs * from subplans (values that are setParam items for those subplans). These * IDs need not be tracked via PlannerParamItems, since we do not need any * duplicate-elimination nor later processing of the represented expressions. * Instead, we just record the assignment of the slot number by incrementing * root->glob->nParamExec. */ typedef struct PlannerParamItem { NodeTag type; Node *item; /* the Var, PlaceHolderVar, or Aggref */ int paramId; /* its assigned PARAM_EXEC slot number */ } PlannerParamItem; /* * When making cost estimates for a SEMI or ANTI join, there are some * correction factors that are needed in both nestloop and hash joins * to account for the fact that the executor can stop scanning inner rows * as soon as it finds a match to the current outer row. These numbers * depend only on the selected outer and inner join relations, not on the * particular paths used for them, so it's worthwhile to calculate them * just once per relation pair not once per considered path. This struct * is filled by compute_semi_anti_join_factors and must be passed along * to the join cost estimation functions. * * outer_match_frac is the fraction of the outer tuples that are * expected to have at least one match. * match_count is the average number of matches expected for * outer tuples that have at least one match. */ typedef struct SemiAntiJoinFactors { Selectivity outer_match_frac; Selectivity match_count; } SemiAntiJoinFactors; /* * For speed reasons, cost estimation for join paths is performed in two * phases: the first phase tries to quickly derive a lower bound for the * join cost, and then we check if that's sufficient to reject the path. * If not, we come back for a more refined cost estimate. The first phase * fills a JoinCostWorkspace struct with its preliminary cost estimates * and possibly additional intermediate values. The second phase takes * these values as inputs to avoid repeating work. * * (Ideally we'd declare this in cost.h, but it's also needed in pathnode.h, * so seems best to put it here.) */ typedef struct JoinCostWorkspace { /* Preliminary cost estimates --- must not be larger than final ones! */ Cost startup_cost; /* cost expended before fetching any tuples */ Cost total_cost; /* total cost (assuming all tuples fetched) */ /* Fields below here should be treated as private to costsize.c */ Cost run_cost; /* non-startup cost components */ /* private for cost_nestloop code */ Cost inner_rescan_run_cost; double outer_matched_rows; Selectivity inner_scan_frac; /* private for cost_mergejoin code */ Cost inner_run_cost; double outer_rows; double inner_rows; double outer_skip_rows; double inner_skip_rows; /* private for cost_hashjoin code */ int numbuckets; int numbatches; } JoinCostWorkspace; #endif /* RELATION_H */
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