/*-------------------------------------------------------------------------
*
* relation.h
- * Definitions for internal planner nodes.
+ * Definitions for planner's internal data structures.
*
*
- * Copyright (c) 1994, Regents of the University of California
+ * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
*
- * $Id: relation.h,v 1.30 1999/05/12 15:02:08 wieck Exp $
+ * $PostgreSQL: pgsql/src/include/nodes/relation.h,v 1.95 2004/06/01 03:03:05 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#ifndef RELATION_H
#define RELATION_H
-#include <nodes/parsenodes.h>
-#include <nodes/primnodes.h>
+#include "access/sdir.h"
+#include "nodes/bitmapset.h"
+#include "nodes/parsenodes.h"
+
/*
* Relids
- * List of relation identifiers (indexes into the rangetable).
+ * Set of relation identifiers (indexes into the rangetable).
*/
-typedef List *Relids;
+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;
+
+/*----------
* RelOptInfo
- * Per-base-relation information
- *
- * 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 - List of relation indentifiers
- * indexed - true if the relation has secondary indices
- * pages - number of pages in the relation
- * tuples - number of tuples in the relation
- * size - number of tuples in the relation after restrictions clauses
- * have been applied
- * width - number of bytes per tuple in the relation after the
- * appropriate projections have been done
- * targetlist - List of TargetList nodes
- * pathlist - List of Path nodes, one for each possible method of
- * generating the relation
- * cheapestpath - least expensive Path (regardless of final order)
- * pruneable - flag to let the planner know whether it can prune the plan
- * space of this RelOptInfo or not.
- *
- * * If the relation is a (secondary) index it will have the following
- * three fields:
- *
- * classlist - List of PG_AMOPCLASS OIDs for the index
- * indexkeys - List of base-relation attribute numbers that are index keys
- * ordering - List of PG_OPERATOR OIDs which order the indexscan result
- * relam - the OID of the pg_am of the index
- *
- * * The presence of the remaining fields depends on the restrictions
- * and joins which the relation participates in:
- *
- * restrictinfo - List of RestrictInfo nodes, containing info about each
- * qualification clause in which this relation participates
+ * 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 Query's
+ * base_rel_list 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 stored
+ * in other_rel_list not base_rel_list.
+ *
+ * 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)
+ * 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 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 JoinInfo nodes, containing info about each join
* clause in which this relation participates
- * innerjoin - List of Path nodes that represent indices that may be used
- * as inner paths of nestloop joins
+ * 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 lists, because those are 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.
*
- * NB. the last element of the arrays classlist, indexkeys and ordering
- * is always 0. 2/95 - ay
+ * 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;
- /* all relations: */
- Relids relids; /* integer list of base relids involved */
+ RelOptKind reloptkind;
+
+ /* all relations included in this RelOptInfo */
+ Relids relids; /* set of base relids (rangetable indexes) */
- /* catalog statistics information */
- bool indexed;
- int pages;
- int tuples;
- int size;
- int width;
+ /* size estimates generated by planner */
+ double rows; /* estimated number of result tuples */
+ int width; /* estimated avg width of result tuples */
/* materialization information */
- List *targetlist;
+ List *reltargetlist; /* needed Vars */
List *pathlist; /* Path structures */
- struct Path *cheapestpath;
- bool pruneable;
-
- /* used solely by indices: */
- Oid *classlist; /* classes of AM operators */
- int *indexkeys; /* keys over which we're indexing */
- Oid relam; /* OID of the access method (in pg_am) */
-
- Oid indproc;
- List *indpred;
+ 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;
+ long pages;
+ double tuples;
+ struct Plan *subplan; /* if subquery */
/* used by various scans and joins: */
- Oid *ordering; /* OID of operators in sort order */
- List *restrictinfo; /* RestrictInfo structures */
+ List *baserestrictinfo; /* RestrictInfo structures (if
+ * base rel) */
+ QualCost baserestrictcost; /* cost of evaluating the above */
+ Relids outerjoinset; /* set of base relids */
List *joininfo; /* JoinInfo structures */
- List *innerjoin;
+
+ /* 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;
-extern Var *get_expr(TargetEntry *foo);
-extern Var *get_groupclause_expr(GroupClause *groupClause, List *targetList);
+/*
+ * 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 MergeOrder
+typedef struct IndexOptInfo
{
NodeTag type;
- Oid join_operator;
- Oid left_operator;
- Oid right_operator;
- Oid left_type;
- Oid right_type;
-} MergeOrder;
-
-typedef enum OrderType
-{
- MERGE_ORDER, SORTOP_ORDER
-} OrderType;
-typedef struct PathOrder
+ Oid indexoid; /* OID of the index relation */
+
+ /* statistics from pg_class */
+ long 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 */
+
+ /* cached info about inner indexscan paths for index */
+ Relids outer_relids; /* other relids in usable join clauses */
+ List *inner_paths; /* List of InnerIndexscanInfo nodes */
+} 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 the top of optimizer/path/pathkeys.c
+ * for more information.)
+ */
+
+typedef struct PathKeyItem
{
NodeTag type;
- OrderType ordtype;
- union
- {
- Oid *sortop;
- MergeOrder *merge;
- } ord;
-} PathOrder;
+ 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;
- RelOptInfo *parent;
- Cost path_cost;
+ NodeTag pathtype; /* tag identifying scan/join method */
- NodeTag pathtype;
+ RelOptInfo *parent; /* the relation this path can build */
- PathOrder *pathorder;
+ /* 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; /* This is a List of List of Var nodes.
- * See the top of optimizer/path/pathkeys.c
- * for more information.
- */
- Cost outerjoincost;
- Relids joinid;
- List *loc_restrictinfo;
+ 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. Although an indexscan can only read
+ * a single relation, it can scan it more than once, potentially using a
+ * different index during each scan. The result is the union (OR) of all the
+ * tuples matched during any scan. (The executor is smart enough not to return
+ * the same tuple more than once, even if it is matched in multiple scans.)
+ *
+ * 'indexinfo' is a list of IndexOptInfo nodes, one per scan to be performed.
+ *
+ * 'indexclauses' is a list of index qualifications, also one per scan.
+ * Each entry in 'indexclauses' is a sublist of qualification clauses to be
+ * used for that scan, with implicit AND semantics across the sublist items.
+ * NOTE that the semantics of the top-level list in 'indexclauses' is OR
+ * combination, while the sublists are implicitly AND combinations!
+ *
+ * 'indexquals' has the same structure as 'indexclauses', but it contains
+ * the actual indexqual conditions that can be used with the index(es).
+ * 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'.
+ *
+ * Both 'indexclauses' and 'indexquals' are lists of sublists of RestrictInfo
+ * nodes. (Before 7.5, we kept bare operator expressions in these lists, but
+ * storing RestrictInfos is more efficient since selectivities can be cached.)
+ *
+ * '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.)
+ *
+ * '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;
- List *indexid;
- List *indexqual;
- int *indexkeys; /* to transform heap attnos into index ones */
+ List *indexinfo;
+ List *indexclauses;
+ List *indexquals;
+ bool isjoininner;
+ ScanDirection indexscandir;
+ double rows; /* estimated number of result tuples */
} IndexPath;
-typedef struct NestPath
+/*
+ * 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 *pathinfo;
- Path *outerjoinpath;
- Path *innerjoinpath;
-} NestPath;
+ List *tideval; /* qual(s) involving CTID = something */
+} TidPath;
-typedef NestPath JoinPath;
+/*
+ * AppendPath represents an Append plan, ie, successive execution of
+ * several member plans. Currently it is only used to handle expansion
+ * of inheritance trees.
+ */
+typedef struct AppendPath
+{
+ Path path;
+ List *subpaths; /* list of component Paths */
+} AppendPath;
+
+/*
+ * ResultPath represents use of a Result plan node, either to compute a
+ * variable-free targetlist or to gate execution of a subplan with a
+ * one-time (variable-free) qual condition. Note that in the former case
+ * path.parent will be NULL; in the latter case it is copied from the subpath.
+ *
+ * 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;
- List *outersortkeys;
- List *innersortkeys;
+ 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;
- List *outerhashkeys;
- List *innerhashkeys;
+ List *path_hashclauses; /* join clauses used for hashing */
} HashPath;
/*
- * Keys
+ * 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 lists 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 the qual will appear in JoinInfo lists
+ * that reference 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
+ * specific set of base rels that it uses (or that the JoinInfo structures
+ * claim it uses). 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.
+ *
+ * We also store a valid_everywhere flag, which says that the clause is not
+ * affected by any lower-level outer join, and therefore any conditions it
+ * asserts can be presumed true throughout the plan tree.
+ *
+ * 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 OrderKey
+typedef struct RestrictInfo
{
NodeTag type;
- int attribute_number;
- Index array_index;
-} OrderKey;
-typedef struct JoinKey
-{
- NodeTag type;
- Var *outer;
- Var *inner;
-} JoinKey;
+ Expr *clause; /* the represented clause of WHERE or JOIN */
-/*
- * clause info
- */
+ bool is_pushed_down; /* TRUE if clause was pushed down in level */
-typedef struct RestrictInfo
-{
- NodeTag type;
- Expr *clause; /* should be an OP clause */
- Cost selectivity;
- bool notclause;
- List *indexids;
+ bool valid_everywhere; /* TRUE if valid on every level */
- /* mergejoin only */
- MergeOrder *mergejoinorder;
+ /*
+ * 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;
- /* hashjoin only */
- Oid hashjoinoperator;
- Relids restrictinfojoinid;
-} RestrictInfo;
+ /* The set of relids (varnos) referenced in the clause: */
+ Relids clause_relids;
-typedef struct JoinMethod
-{
- NodeTag type;
- List *jmkeys;
- List *clauses;
-} JoinMethod;
+ /* 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 */
-typedef struct HashInfo
-{
- JoinMethod jmethod;
- Oid hashop;
-} HashInfo;
+ /* This field is NULL unless clause is an OR clause: */
+ Expr *orclause; /* modified clause with RestrictInfos */
-typedef struct MergeInfo
-{
- JoinMethod jmethod;
- MergeOrder *m_ordering;
-} MergeInfo;
+ /* 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;
+
+/*
+ * Join clause info.
+ *
+ * We make a list of these for each RelOptInfo, containing info about
+ * all the join clauses this RelOptInfo participates in. (For this
+ * purpose, a "join clause" is a WHERE clause that mentions both vars
+ * belonging to this relation and vars belonging to relations not yet
+ * joined to it.) We group these clauses according to the set of
+ * other base relations (unjoined relations) mentioned in them.
+ * There is one JoinInfo for each distinct set of unjoined_relids,
+ * and its jinfo_restrictinfo lists the clause(s) that use that set
+ * of other relations.
+ */
typedef struct JoinInfo
{
NodeTag type;
- Relids unjoined_relids;
- List *jinfo_restrictinfo;
- bool mergejoinable;
- bool hashjoinable;
+ Relids unjoined_relids; /* some rels not yet part of my RelOptInfo */
+ List *jinfo_restrictinfo; /* relevant RestrictInfos */
} JoinInfo;
-typedef struct Iter
+/*
+ * 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 index we compute the set of possible otherrelids (all relids
+ * appearing in joinquals that could become indexquals for this index).
+ * 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 that index. Similarly, for each base relation,
+ * we form the union of the per-index otherrelids sets. Two outer relations
+ * with the same intersection with that set will have the same best overall
+ * inner indexscan for the base relation. We use lists of InnerIndexscanInfo
+ * nodes to cache the results of these searches at both the index and
+ * relation level.
+ *
+ * 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;
- Node *iterexpr;
- Oid itertype; /* type of the iter expr (use for type
- * checking) */
-} Iter;
+ /* 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;
/*
- * Stream:
- * A stream represents a root-to-leaf path in a plan tree (i.e. a tree of
- * JoinPaths and Paths). The stream includes pointers to all Path nodes,
- * as well as to any clauses that reside above Path nodes. This structure
- * is used to make Path nodes and clauses look similar, so that Predicate
- * Migration can run.
- *
- * pathptr -- pointer to the current path node
- * cinfo -- if NULL, this stream node referes to the path node.
- * Otherwise this is a pointer to the current clause.
- * clausetype -- whether cinfo is in loc_restrictinfo or pathinfo in the
- * path node
- * upstream -- linked list pointer upwards
- * downstream -- ditto, downwards
- * groupup -- whether or not this node is in a group with the node upstream
- * groupcost -- total cost of the group that node is in
- * groupsel -- total selectivity of the group that node is in
+ * 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 Query node's in_info_list.
*/
-typedef struct Stream *StreamPtr;
-typedef struct Stream
+typedef struct InClauseInfo
{
NodeTag type;
- Path *pathptr;
- RestrictInfo *cinfo;
- int *clausetype;
- struct Stream *upstream;
- struct Stream *downstream;
- bool groupup;
- Cost groupcost;
- Cost groupsel;
-} Stream;
-
-#endif /* RELATION_H */
+ 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 */
projects / postgresql / blobdiff