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/*-------------------------------------------------------------------------
*
* relation.h
* Definitions for planner's internal data structures.
*
*
* Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/nodes/relation.h,v 1.154.2.4 2009/04/16 20:42:28 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#ifndef RELATION_H
#define RELATION_H
#include "access/sdir.h"
#include "nodes/bitmapset.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;
/*----------
* 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; /* to keep track of cross-level Params */
List *subplans; /* Plans for SubPlan nodes */
List *subrtables; /* Rangetables for SubPlan nodes */
Bitmapset *rewindPlanIDs; /* indices of subplans that require REWIND */
List *finalrtable; /* "flat" rangetable for executor */
List *relationOids; /* OIDs of relations the plan depends on */
bool transientPlan; /* redo plan when TransactionXmin changes? */
} 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 */
/*
* 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 */
/*
* 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 *resultRelations; /* integer list of RT indexes, or NIL */
List *returningLists; /* list of lists of TargetEntry, or NIL */
List *init_plans; /* init subplans for query */
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 *oj_info_list; /* list of OuterJoinInfos */
List *in_info_list; /* list of InClauseInfos */
List *append_rel_list; /* list of AppendRelInfos */
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 */
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 */
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 */
bool hasPseudoConstantQuals; /* true if any RestrictInfo has
* pseudoconstant = true */
} 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.
*
* 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 an Append
* plan comprising the best plans 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 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)
* subrtable - rangetable for subquery (NIL 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 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
* 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.
*----------
*/
typedef enum RelOptKind
{
RELOPT_BASEREL,
RELOPT_JOINREL,
RELOPT_OTHER_MEMBER_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 */
List *subrtable; /* if subquery */
/* 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 */
/* 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.
*
* opfamily[], indexkeys[], opcintype[], fwdsortop[], revsortop[],
* and nulls_first[] each have ncolumns entries.
* Note: for historical reasons, the opfamily array has an extra entry
* that is always zero. Some code scans until it sees a zero entry,
* rather than looking at ncolumns.
*
* Zeroes in the indexkeys[] array indicate index columns that are
* expressions; there is one element in indexprs for each such column.
*
* For an unordered index, the sortop arrays contains zeroes. Note that
* fwdsortop[] and nulls_first[] describe the sort ordering of a forward
* indexscan; we can also consider a backward indexscan, which will
* generate sort order described by revsortop/!nulls_first.
*
* 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 *opfamily; /* OIDs of operator families for columns */
int *indexkeys; /* column numbers of index's keys, or 0 */
Oid *opcintype; /* OIDs of opclass declared input data types */
Oid *fwdsortop; /* OIDs of sort operators for each column */
Oid *revsortop; /* OIDs of sort operators for backward scan */
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 */
bool predOK; /* true if predicate matches query */
bool unique; /* true if a unique index */
bool amoptionalkey; /* can query omit key for the first column? */
bool amsearchnulls; /* can AM search for NULL index entries? */
} 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. (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.)
*
* 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 */
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 inheritance parent relation to represent the corresponding expression
* on an inheritance child. The element should be ignored for all purposes
* except constructing inner-indexscan paths for the child relation. (Other
* types of join are driven from transposed joininfo-list entries.) Note
* that the EC's ec_relids field does NOT include the child relation.
*
* 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 */
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. 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;
/*
* 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 PathKey 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).
* Note that the path costs will be calculated differently from a plain
* indexscan in this case, and in addition there's a special 'rows' value
* different from the parent RelOptInfo's (see below).
*
* '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
*
* 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;
/*
* 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)
/*
* 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;
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.
*
* 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 a
* nullable_relids field, which is the set of rels it 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;
/* 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 this_selec; /* selectivity; -1 if not yet set; >1 means
* a redundant clause */
/* 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 */
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;
/*
* 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 paths 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 indexscans 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 lookup key; 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 paths for this lookup key (NULL if no available indexscans): */
Path *cheapest_startup_innerpath; /* cheapest startup cost */
Path *cheapest_total_innerpath; /* cheapest total cost */
} InnerIndexscanInfo;
/*
* Outer 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 an
* OuterJoinInfo struct. These structs are kept in the PlannerInfo node's
* oj_info_list.
*
* min_lefthand and min_righthand are the sets of base relids that must be
* available on each side when performing the outer join. lhs_strict is
* true if the outer join's condition cannot succeed when the LHS variables
* are all NULL (this means that the 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 outer join. (These are needed to help compute
* min_lefthand and min_righthand for higher joins, but are not used
* thereafter.)
*
* 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.)
*
* Note: OuterJoinInfo directly represents only LEFT JOIN and FULL JOIN;
* RIGHT JOIN is handled by switching the inputs to make it a LEFT JOIN.
* We make an OuterJoinInfo for FULL JOINs even though there is no flexibility
* of planning for them, because this simplifies make_join_rel()'s API.
*/
typedef struct OuterJoinInfo
{
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 */
bool is_full_join; /* it's a FULL OUTER JOIN */
bool lhs_strict; /* joinclause is strict for some LHS rel */
bool delay_upper_joins; /* can't commute with upper RHS */
} OuterJoinInfo;
/*
* 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.
*
* Note: sub_targetlist is a bit misnamed; it is a list of the expressions
* on the RHS of the IN's join clauses. (This normally starts out as a list
* of Vars referencing the subquery outputs, but can get mutated if the
* subquery is flattened into the main query.)
*/
typedef struct InClauseInfo
{
NodeTag type;
Relids lefthand; /* base relids in lefthand expressions */
Relids righthand; /* base relids coming from the subselect */
List *sub_targetlist; /* RHS expressions of the IN's comparisons */
List *in_operators; /* OIDs of the IN's equality operators */
} InClauseInfo;
/*
* 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 the integer column number of the child
* column corresponding to the N'th column of the parent. A list element
* is zero if it corresponds to a dropped column of the parent (this is
* only possible for inheritance cases, not UNION ALL).
*/
List *col_mappings; /* list of child attribute numbers */
/*
* 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).
*
* This might seem redundant with the col_mappings data, but it is handy
* because flattening of sub-SELECTs that are members of a UNION ALL will
* cause changes in the expressions that need to be substituted for a
* parent Var. Adjusting this data structure lets us track what really
* needs to be substituted.
*
* 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;
/*
* glob->paramlist keeps track of the PARAM_EXEC slots that we have decided
* we need for the query. At runtime these slots are used to pass values
* either down into subqueries (for outer references in subqueries) or up out
* of subqueries (for the results of a subplan). The n'th entry in the list
* (n counts from 0) corresponds to Param->paramid = n.
*
* Each paramlist item shows the absolute query level it is associated with,
* where the outermost query is level 1 and nested subqueries have higher
* numbers. The item the parameter slot represents can be one of three kinds:
*
* A Var: the slot represents a variable of that level that must be passed
* down because subqueries have outer references to it. The varlevelsup
* value in the Var will always be zero.
*
* 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.
*
* A Param: the slot holds the result of a subplan (it is a setParam item
* for that subplan). The absolute level shown for such items corresponds
* to the parent query of the subplan.
*
* Note: we detect duplicate Var parameters and coalesce them into one slot,
* but we do not do this for Aggref or Param slots.
*/
typedef struct PlannerParamItem
{
NodeTag type;
Node *item; /* the Var, Aggref, or Param */
Index abslevel; /* its absolute query level */
} PlannerParamItem;
#endif /* RELATION_H */