/*------------------------------------------------------------------------- * * relation.h * Definitions for planner's internal data structures. * * * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * * $PostgreSQL: pgsql/src/include/nodes/relation.h,v 1.119.2.1 2005/11/14 23:54:36 tgl Exp $ * *------------------------------------------------------------------------- */ #ifndef RELATION_H #define RELATION_H #include "access/sdir.h" #include "nodes/bitmapset.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; /*---------- * 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 manipulates * the passed-in Query data structure; someday that should stop. *---------- */ typedef struct PlannerInfo { NodeTag type; Query *parse; /* the Query being planned */ /* * base_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. Note that the array may be * enlarged on-the-fly. */ struct RelOptInfo **base_rel_array; /* All one-relation RelOptInfos */ int base_rel_array_size; /* current allocated array len */ /* * 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 */ List *equi_key_list; /* list of lists of equijoined PathKeyItems */ List *left_join_clauses; /* list of RestrictInfos for outer * join clauses w/nonnullable var on * left */ List *right_join_clauses; /* list of RestrictInfos for outer * join clauses w/nonnullable var on * right */ List *full_join_clauses; /* list of RestrictInfos for full * outer join clauses */ List *in_info_list; /* list of InClauseInfos */ List *query_pathkeys; /* desired pathkeys for query_planner(), and * actual pathkeys afterwards */ List *group_pathkeys; /* groupClause pathkeys, if any */ List *sort_pathkeys; /* sortClause pathkeys, if any */ double tuple_fraction; /* tuple_fraction passed to query_planner */ bool hasJoinRTEs; /* true if any RTEs are RTE_JOIN kind */ bool hasOuterJoins; /* true if any RTEs are outer joins */ bool hasHavingQual; /* true if havingQual was non-null */ } PlannerInfo; /*---------- * 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 * base_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. * * Currently the only kind of otherrels are those made for child relations * of an inheritance scan (SELECT FROM foo*). The parent table's RTE and * corresponding baserel represent the whole result of the inheritance scan. * The planner creates separate RTEs and associated RelOptInfos for each child * table (including the parent table, in its capacity as a member of the * inheritance set). These RelOptInfos are physically identical to baserels, * but are otherrels because they are not in the main join tree. These added * RTEs and otherrels are used to plan the scans of the individual tables in * the inheritance set; then the parent baserel is given an Append plan * comprising the best plans for the individual child tables. * * 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 nodes for the attributes we need to * output from this relation (in no particular order) * NOTE: in a child relation, may contain RowExprs * pathlist - List of Path nodes, one for each potentially useful * method of generating the relation * cheapest_startup_path - the pathlist member with lowest startup cost * (regardless of its ordering) * cheapest_total_path - the pathlist member with lowest total cost * (regardless of its ordering) * cheapest_unique_path - for caching cheapest path to produce unique * (no duplicates) output from relation * * 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) * subplan - plan for subquery (NULL if it's not a subquery) * * Note: for a subquery, tuples and subplan are not set immediately * upon creation of the RelOptInfo object; they are filled in when * set_base_rel_pathlist processes the object. * * For otherrels that are inheritance children, 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) * outerjoinset - For a base rel: if the rel appears within the nullable * side of an outer join, the set of all relids * participating in the highest such outer join; else NULL. * Otherwise, unused. * joininfo - List of RestrictInfo nodes, containing info about each * join clause in which this relation participates * index_outer_relids - only used for base rels; set of outer relids * that participate in indexable joinclauses for this rel * index_inner_paths - only used for base rels; list of InnerIndexscanInfo * nodes showing best indexpaths for various subsets of * index_outer_relids. * * 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. * * outerjoinset is used to ensure correct placement of WHERE clauses that * apply to outer-joined relations; we must not apply such WHERE clauses * until after the outer join is performed. *---------- */ typedef enum RelOptKind { RELOPT_BASEREL, RELOPT_JOINREL, RELOPT_OTHER_CHILD_REL } 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; /* needed Vars */ List *pathlist; /* Path structures */ struct Path *cheapest_startup_path; struct Path *cheapest_total_path; struct Path *cheapest_unique_path; /* information about a base rel (not set for join rels!) */ Index relid; 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; BlockNumber pages; double tuples; struct Plan *subplan; /* if subquery */ /* used by various scans and joins: */ List *baserestrictinfo; /* RestrictInfo structures (if base * rel) */ QualCost baserestrictcost; /* cost of evaluating the above */ Relids outerjoinset; /* set of base relids */ List *joininfo; /* RestrictInfo structures for join clauses * involving this rel */ /* cached info about inner indexscan paths for relation: */ Relids index_outer_relids; /* other relids in indexable join * clauses */ List *index_inner_paths; /* InnerIndexscanInfo nodes */ /* * Inner indexscans are not in the main pathlist because they are not * usable except in specific join contexts. We use the index_inner_paths * list just to avoid recomputing the best inner indexscan repeatedly for * similar outer relations. See comments for InnerIndexscanInfo. */ } RelOptInfo; /* * IndexOptInfo * Per-index information for planning/optimization * * Prior to Postgres 7.0, RelOptInfo was used to describe both relations * and indexes, but that created confusion without actually doing anything * useful. So now we have a separate IndexOptInfo struct for indexes. * * classlist[], indexkeys[], and ordering[] have ncolumns entries. * Zeroes in the indexkeys[] array indicate index columns that are * expressions; there is one element in indexprs for each such column. * * Note: for historical reasons, the classlist and ordering arrays have * an extra entry that is always zero. Some code scans until it sees a * zero entry, rather than looking at ncolumns. * * 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. */ typedef struct IndexOptInfo { NodeTag type; Oid indexoid; /* OID of the index relation */ 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 */ Oid *classlist; /* OIDs of operator classes for columns */ int *indexkeys; /* column numbers of index's keys, or 0 */ Oid *ordering; /* OIDs of sort operators for each column */ 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 */ bool predOK; /* true if predicate matches query */ bool unique; /* true if a unique index */ bool amoptionalkey; /* can query omit key for the first column? */ } IndexOptInfo; /* * PathKeys * * The sort ordering of a path is represented by a list of sublists of * PathKeyItem nodes. An empty list implies no known ordering. Otherwise * the first sublist represents the primary sort key, the second the * first secondary sort key, etc. Each sublist contains one or more * PathKeyItem nodes, each of which can be taken as the attribute that * appears at that sort position. (See optimizer/README for more * information.) */ typedef struct PathKeyItem { NodeTag type; Node *key; /* the item that is ordered */ Oid sortop; /* the ordering operator ('<' op) */ /* * key typically points to a Var node, ie a relation attribute, but it can * also point to an arbitrary expression representing the value indexed by * an index expression. */ } PathKeyItem; /* * Type "Path" is used as-is for sequential-scan paths. For other * path types it is the first component of a larger struct. * * Note: "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 where there is no need * to distinguish the Plan type during path processing. */ typedef struct Path { NodeTag type; NodeTag pathtype; /* tag identifying scan/join method */ RelOptInfo *parent; /* the relation this path can build */ /* estimated execution costs for path (see costsize.c for more info) */ 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 Lists of PathKeyItem nodes; see above */ } Path; /*---------- * IndexPath represents an index scan over a single index. * * '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. * * 'indexquals' has the same structure as 'indexclauses', but it contains * the actual indexqual 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'. * * 'isjoininner' is TRUE if the path is a nestloop inner scan (that is, * some of the index conditions are join rather than restriction clauses). * * '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 plan type. * * 'rows' is the estimated result tuple count for the indexscan. This * is the same as path.parent->rows for a simple indexscan, but it is * different for a nestloop inner scan, because the additional indexquals * coming from join clauses make the scan more selective than the parent * rel's restrict clauses alone would do. *---------- */ typedef struct IndexPath { Path path; IndexOptInfo *indexinfo; List *indexclauses; List *indexquals; bool isjoininner; ScanDirection indexscandir; Cost indextotalcost; Selectivity indexselectivity; double rows; /* estimated number of result tuples */ } 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 IndexScan 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 IndexScan. The costs of a BitmapIndexScan * can be computed using the IndexPath's indextotalcost and indexselectivity. * * BitmapHeapPaths can be nestloop inner indexscans. The isjoininner and * rows fields serve the same purpose as for plain IndexPaths. */ typedef struct BitmapHeapPath { Path path; Path *bitmapqual; /* IndexPath, BitmapAndPath, BitmapOrPath */ bool isjoininner; /* T if it's a nestloop inner scan */ double rows; /* estimated number of result tuples */ } 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 * * tideval is an implicitly OR'ed list of quals of the form CTID = something. * Note they are bare quals, not RestrictInfos. */ typedef struct TidPath { Path path; List *tideval; /* qual(s) involving CTID = something */ } TidPath; /* * AppendPath represents an Append plan, ie, successive execution of * several member plans. Currently it is only used to handle expansion * of inheritance trees. * * Note: it is possible for "subpaths" to contain only one, or even no, * elements. These cases are optimized during create_append_plan. */ typedef struct AppendPath { Path path; List *subpaths; /* list of component Paths */ } AppendPath; /* * ResultPath represents use of a Result plan node. There are several * applications for this: * * To compute a variable-free targetlist (a "SELECT expressions" query). * In this case subpath and path.parent will both be NULL. constantqual * might or might not be empty ("SELECT expressions WHERE something"). * * To gate execution of a subplan with a one-time (variable-free) qual * condition. path.parent is copied from the subpath. * * To substitute for a scan plan when we have proven that no rows in * a table will satisfy the query. subpath is NULL but path.parent * references the not-to-be-scanned relation, and constantqual is * a constant FALSE. * * Note that constantqual is a list of bare clauses, not RestrictInfos. */ typedef struct ResultPath { Path path; Path *subpath; List *constantqual; } 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; double rows; /* estimated number of result tuples */ } 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 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. * * 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 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 */ } 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 */ } 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. * * 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, and any quals appearing in WHERE or * in a JOIN above the outer join cannot be pushed down below the outer join. * Otherwise the outer join will produce wrong results because it will see the * wrong sets of input rows. All quals are stored as RestrictInfo nodes * during planning, but there's 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 appearing in 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 higher 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 came from a point above the join of the * set of base rels listed in required_relids. A clause that originally came * from WHERE will *always* have its is_pushed_down flag set; a clause that * came from an INNER JOIN condition, but doesn't use all the rels being * joined, will also have is_pushed_down set because it will get attached to * some lower joinrel. * * When application of a qual must be delayed by outer join, we also mark it * with outerjoin_delayed = true. This isn't redundant with required_relids * because that might equal clause_relids whether or not it's an outer-join * clause. * * 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 fairly limited --- 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. */ 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 outer join */ /* * This 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.) */ bool can_join; /* 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; /* 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 */ /* cache space for cost and selectivity */ QualCost eval_cost; /* eval cost of clause; -1 if not yet set */ Selectivity this_selec; /* selectivity; -1 if not yet set */ /* valid if clause is mergejoinable, else InvalidOid: */ Oid mergejoinoperator; /* copy of clause operator */ Oid left_sortop; /* leftside sortop needed for mergejoin */ Oid right_sortop; /* rightside sortop needed for mergejoin */ /* cache space for mergeclause processing; NIL if not yet set */ List *left_pathkey; /* canonical pathkey for left side */ List *right_pathkey; /* canonical pathkey for right side */ /* cache space for mergeclause processing; -1 if not yet set */ Selectivity left_mergescansel; /* fraction of left side to scan */ Selectivity right_mergescansel; /* fraction of right side to scan */ /* 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; /* * Inner indexscan info. * * An inner indexscan is one that uses one or more joinclauses as index * conditions (perhaps in addition to plain restriction clauses). So it * can only be used as the inner path of a nestloop join where the outer * relation includes all other relids appearing in those joinclauses. * The set of usable joinclauses, and thus the best inner indexscan, * thus varies depending on which outer relation we consider; so we have * to recompute the best such path for every join. To avoid lots of * redundant computation, we cache the results of such searches. For * each relation we compute the set of possible otherrelids (all relids * appearing in joinquals that could become indexquals for this table). * Two outer relations whose relids have the same intersection with this * set will have the same set of available joinclauses and thus the same * best inner indexscan for the inner relation. By taking the intersection * before scanning the cache, we avoid recomputing when considering * join rels that differ only by the inclusion of irrelevant other rels. * * The search key also includes a bool showing whether the join being * considered is an outer join. Since we constrain the join order for * outer joins, I believe that this bool can only have one possible value * for any particular base relation; but store it anyway to avoid confusion. */ typedef struct InnerIndexscanInfo { NodeTag type; /* The lookup key: */ Relids other_relids; /* a set of relevant other relids */ bool isouterjoin; /* true if join is outer */ /* Best path for this lookup key: */ Path *best_innerpath; /* best inner indexscan, or NULL if none */ } InnerIndexscanInfo; /* * IN clause info. * * When we convert top-level IN quals into join operations, we must restrict * the order of joining and use special join methods at some join points. * We record information about each such IN clause in an InClauseInfo struct. * These structs are kept in the PlannerInfo node's in_info_list. */ typedef struct InClauseInfo { NodeTag type; Relids lefthand; /* base relids in lefthand expressions */ Relids righthand; /* base relids coming from the subselect */ List *sub_targetlist; /* targetlist of original RHS subquery */ /* * Note: sub_targetlist is just a list of Vars or expressions; it does not * contain TargetEntry nodes. */ } InClauseInfo; #endif /* RELATION_H */