[pg-rex/syncrep.git] / src / include / nodes / relation.h

/*-------------------------------------------------------------------------
 *
 * relation.h
 *        Definitions for internal planner nodes.
 *
 *
 * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * $Id: relation.h,v 1.66 2002/08/19 15:08:47 tgl Exp $
 *
 *-------------------------------------------------------------------------
 */
#ifndef RELATION_H
#define RELATION_H

#include "access/sdir.h"
#include "nodes/parsenodes.h"

/*
 * Relids
 *              List of relation identifiers (indexes into the rangetable).
 *
 *              Note: these are lists of integers, not Nodes.
 */

typedef List *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;

/*----------
 * 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 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.  An otherrel is created for each
 * join RTE as an aid in processing Vars that refer to the join's outputs,
 * but it serves no other purpose in planning.  It is important not to
 * confuse this otherrel with the joinrel that represents the matching set
 * of base relations.
 *
 * A second category 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.
 *
 * 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 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)
 *              targetlist - List of TargetEntry nodes for the attributes we need
 *                                       to output from this relation
 *              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)
 *              pruneable - flag to let the planner know whether it can prune the
 *                                      pathlist of this RelOptInfo or not.
 *
 * If the relation is a base relation it will have these fields set:
 *
 *              rtekind - distinguishes plain relation, subquery, or function RTE
 *              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.  In otherrels for join RTEs, these fields
 *              are empty --- the only useful field of a join otherrel is its
 *              outerjoinset.
 *
 * If the relation is a join relation it will have these fields set:
 *
 *              joinrti - RT index of corresponding JOIN RTE, if any; 0 if none
 *              joinrteids - List of RT indexes of JOIN RTEs included in this join
 *                                       (including joinrti)
 *
 * 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 list of all relids
 *                                      participating in the highest such outer join; else NIL.
 *                                      For a join otherrel: the list of all baserel relids
 *                                      syntactically within the join.  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. This field is non-null
 *                                      only for base rels, since join rels have no indices.
 *
 * 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.
 *
 * 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_JOIN_REL,
        RELOPT_OTHER_CHILD_REL
} RelOptKind;

typedef struct RelOptInfo
{
        NodeTag         type;

        RelOptKind      reloptkind;

        /* all relations included in this RelOptInfo */
        Relids          relids;                 /* integer list of base relids (RT
                                                                 * indexes) */

        /* 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       *pathlist;           /* Path structures */
        struct Path *cheapest_startup_path;
        struct Path *cheapest_total_path;
        bool            pruneable;

        /* information about a base rel (not set for join rels!) */
        RTEKind         rtekind;                /* RELATION, SUBQUERY, or FUNCTION */
        List       *indexlist;
        long            pages;
        double          tuples;
        struct Plan *subplan;           /* if subquery */

        /* information about a join rel (not set for base rels!) */
        Index           joinrti;
        List       *joinrteids;

        /* used by various scans and joins: */
        List       *baserestrictinfo;           /* RestrictInfo structures (if
                                                                                 * base rel) */
        Cost            baserestrictcost;               /* cost of evaluating the above */
        Relids          outerjoinset;   /* integer list of base relids */
        List       *joininfo;           /* JoinInfo structures */
        List       *innerjoin;          /* potential indexscans for nestloop joins */

        /*
         * innerjoin indexscans are not in the main pathlist because they are
         * not usable except in specific join contexts; we have to test before
         * seeing whether they can be used.
         */
} 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.
 *
 *              indexoid  - OID of the index relation itself
 *              pages     - number of disk pages in index
 *              tuples    - number of index tuples in index
 *              ncolumns  - number of columns in index
 *              nkeys     - number of keys used by index (input columns)
 *              classlist - List of PG_OPCLASS 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
 *              amcostestimate - OID of the relam's cost estimator
 *              indproc   - OID of the function if a functional index, else 0
 *              indpred   - index predicate if a partial index, else NULL
 *              unique    - true if index is unique
 *
 *              ncolumns and nkeys are the same except for a functional index,
 *              wherein ncolumns is 1 (the single function output) while nkeys
 *              is the number of table columns passed to the function. classlist[]
 *              and ordering[] have ncolumns entries, while indexkeys[] has nkeys
 *              entries.
 *
 *              Note: for historical reasons, the arrays classlist, indexkeys and
 *              ordering have an extra entry that is always zero.  Some code scans
 *              until it sees a zero rather than looking at ncolumns or nkeys.
 */

typedef struct IndexOptInfo
{
        NodeTag         type;

        Oid                     indexoid;               /* OID of the index relation */

        /* statistics from pg_class */
        long            pages;
        double          tuples;

        /* index descriptor information */
        int                     ncolumns;               /* number of columns in index */
        int                     nkeys;                  /* number of keys used by index */
        Oid                *classlist;          /* AM operator classes for columns */
        int                *indexkeys;          /* column numbers of index's keys */
        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 */

        Oid                     indproc;                /* if a functional index */
        List       *indpred;            /* if a partial index */
        bool            unique;                 /* if a unique index */
} IndexOptInfo;


/*
 * A Var is considered to belong to a relation if it's either from one
 * of the actual base rels making up the relation, or it's a join alias
 * var that is included in the relation.
 */
#define VARISRELMEMBER(varno,rel) (intMember((varno), (rel)->relids) || \
                                                                   intMember((varno), (rel)->joinrteids))


/*
 * 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;

        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 a Func clause representing the value indexed by a
         * functional index.  Someday we might allow arbitrary expressions as
         * path keys, so don't assume more than you must.
         */
} PathKeyItem;

/*
 * Type "Path" is used as-is for sequential-scan paths.  For other
 * path types it is the first component of a larger struct.
 */

typedef struct Path
{
        NodeTag         type;

        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) */

        NodeTag         pathtype;               /* tag identifying scan/join method */
        /* XXX why is pathtype separate from the NodeTag? */

        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.
 *
 * 'indexqual' is a list of index qualifications, also one per scan.
 * Each entry in 'indexqual' is a sublist of qualification expressions with
 * implicit AND semantics across the sublist items.  Only expressions that
 * are usable as indexquals (as determined by indxpath.c) may appear here.
 * NOTE that the semantics of the top-level list in 'indexqual' is OR
 * combination, while the sublists are implicitly AND combinations!
 * Also note that indexquals lists do not contain RestrictInfo nodes,
 * just bare clause expressions.
 *
 * '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.)
 *
 * 'joinrelids' is only used in IndexPaths that are constructed for use
 * as the inner path of a nestloop join.  These paths have indexquals
 * that refer to values of other rels, so those other rels must be
 * included in the outer joinrel in order to make a usable join.
 *
 * 'alljoinquals' is also used only for inner paths of nestloop joins.
 * This flag is TRUE iff all the indexquals came from non-pushed-down
 * JOIN/ON conditions, which means the path is safe to use for an outer join.
 *
 * '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 path, 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       *indexinfo;
        List       *indexqual;
        ScanDirection indexscandir;
        Relids          joinrelids;             /* other rels mentioned in indexqual */
        bool            alljoinquals;   /* all indexquals derived from JOIN conds? */
        double          rows;                   /* estimated number of result tuples */
} IndexPath;

/*
 * TidPath represents a scan by TID
 */
typedef struct TidPath
{
        Path            path;
        List       *tideval;
        Relids          unjoined_relids;        /* some rels not yet part of my Path */
} TidPath;

/*
 * 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;

/*
 * 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.      (Before 7.0, this was a list of bare
 * clause expressions, but we can save on list memory and cost_qual_eval
 * work by leaving it in the form of a RestrictInfo list.)
 *
 * 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.
 * (But note that path_hashclauses will always be a one-element list,
 * since we only hash on one hashable clause.)
 *
 * 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 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 ispusheddown 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
 * ispusheddown flag set; a clause that came from an INNER JOIN condition,
 * but doesn't use all the rels being joined, will also have ispusheddown set
 * because it will get attached to some lower joinrel.
 *
 * 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...)
 */

typedef struct RestrictInfo
{
        NodeTag         type;

        Expr       *clause;                     /* the represented clause of WHERE or JOIN */

        bool            ispusheddown;   /* TRUE if clause was pushed down in level */

        /* only used if clause is an OR clause: */
        List       *subclauseindices;           /* indexes matching subclauses */
        /* subclauseindices is a List of Lists of IndexOptInfos */

        /* cache space for costs (currently only used for join clauses) */
        Cost            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;        /* some rels not yet part of my RelOptInfo */
        List       *jinfo_restrictinfo;         /* relevant RestrictInfos */
} JoinInfo;

#endif   /* RELATION_H */