Adding upstream version 14.5.upstream/14.5upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 528 insertions, 0 deletions

diff --git a/src/backend/optimizer/path/tidpath.c b/src/backend/optimizer/path/tidpath.c
new file mode 100644
index 0000000..0725d95
--- /dev/null
+++ b/src/backend/optimizer/path/tidpath.c
@@ -0,0 +1,528 @@
+/*-------------------------------------------------------------------------
+ *
+ * tidpath.c
+ *	  Routines to determine which TID conditions are usable for scanning
+ *	  a given relation, and create TidPaths and TidRangePaths accordingly.
+ *
+ * For TidPaths, we look for WHERE conditions of the form
+ * "CTID = pseudoconstant", which can be implemented by just fetching
+ * the tuple directly via heap_fetch().  We can also handle OR'd conditions
+ * such as (CTID = const1) OR (CTID = const2), as well as ScalarArrayOpExpr
+ * conditions of the form CTID = ANY(pseudoconstant_array).  In particular
+ * this allows
+ *		WHERE ctid IN (tid1, tid2, ...)
+ *
+ * As with indexscans, our definition of "pseudoconstant" is pretty liberal:
+ * we allow anything that doesn't involve a volatile function or a Var of
+ * the relation under consideration.  Vars belonging to other relations of
+ * the query are allowed, giving rise to parameterized TID scans.
+ *
+ * We also support "WHERE CURRENT OF cursor" conditions (CurrentOfExpr),
+ * which amount to "CTID = run-time-determined-TID".  These could in
+ * theory be translated to a simple comparison of CTID to the result of
+ * a function, but in practice it works better to keep the special node
+ * representation all the way through to execution.
+ *
+ * Additionally, TidRangePaths may be created for conditions of the form
+ * "CTID relop pseudoconstant", where relop is one of >,>=,<,<=, and
+ * AND-clauses composed of such conditions.
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/optimizer/path/tidpath.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/sysattr.h"
+#include "catalog/pg_operator.h"
+#include "catalog/pg_type.h"
+#include "nodes/nodeFuncs.h"
+#include "optimizer/clauses.h"
+#include "optimizer/optimizer.h"
+#include "optimizer/pathnode.h"
+#include "optimizer/paths.h"
+#include "optimizer/restrictinfo.h"
+
+
+/*
+ * Does this Var represent the CTID column of the specified baserel?
+ */
+static inline bool
+IsCTIDVar(Var *var, RelOptInfo *rel)
+{
+	/* The vartype check is strictly paranoia */
+	if (var->varattno == SelfItemPointerAttributeNumber &&
+		var->vartype == TIDOID &&
+		var->varno == rel->relid &&
+		var->varlevelsup == 0)
+		return true;
+	return false;
+}
+
+/*
+ * Check to see if a RestrictInfo is of the form
+ *		CTID OP pseudoconstant
+ * or
+ *		pseudoconstant OP CTID
+ * where OP is a binary operation, the CTID Var belongs to relation "rel",
+ * and nothing on the other side of the clause does.
+ */
+static bool
+IsBinaryTidClause(RestrictInfo *rinfo, RelOptInfo *rel)
+{
+	OpExpr	   *node;
+	Node	   *arg1,
+			   *arg2,
+			   *other;
+	Relids		other_relids;
+
+	/* Must be an OpExpr */
+	if (!is_opclause(rinfo->clause))
+		return false;
+	node = (OpExpr *) rinfo->clause;
+
+	/* OpExpr must have two arguments */
+	if (list_length(node->args) != 2)
+		return false;
+	arg1 = linitial(node->args);
+	arg2 = lsecond(node->args);
+
+	/* Look for CTID as either argument */
+	other = NULL;
+	other_relids = NULL;
+	if (arg1 && IsA(arg1, Var) &&
+		IsCTIDVar((Var *) arg1, rel))
+	{
+		other = arg2;
+		other_relids = rinfo->right_relids;
+	}
+	if (!other && arg2 && IsA(arg2, Var) &&
+		IsCTIDVar((Var *) arg2, rel))
+	{
+		other = arg1;
+		other_relids = rinfo->left_relids;
+	}
+	if (!other)
+		return false;
+
+	/* The other argument must be a pseudoconstant */
+	if (bms_is_member(rel->relid, other_relids) ||
+		contain_volatile_functions(other))
+		return false;
+
+	return true;				/* success */
+}
+
+/*
+ * Check to see if a RestrictInfo is of the form
+ *		CTID = pseudoconstant
+ * or
+ *		pseudoconstant = CTID
+ * where the CTID Var belongs to relation "rel", and nothing on the
+ * other side of the clause does.
+ */
+static bool
+IsTidEqualClause(RestrictInfo *rinfo, RelOptInfo *rel)
+{
+	if (!IsBinaryTidClause(rinfo, rel))
+		return false;
+
+	if (((OpExpr *) rinfo->clause)->opno == TIDEqualOperator)
+		return true;
+
+	return false;
+}
+
+/*
+ * Check to see if a RestrictInfo is of the form
+ *		CTID OP pseudoconstant
+ * or
+ *		pseudoconstant OP CTID
+ * where OP is a range operator such as <, <=, >, or >=, the CTID Var belongs
+ * to relation "rel", and nothing on the other side of the clause does.
+ */
+static bool
+IsTidRangeClause(RestrictInfo *rinfo, RelOptInfo *rel)
+{
+	Oid			opno;
+
+	if (!IsBinaryTidClause(rinfo, rel))
+		return false;
+	opno = ((OpExpr *) rinfo->clause)->opno;
+
+	if (opno == TIDLessOperator || opno == TIDLessEqOperator ||
+		opno == TIDGreaterOperator || opno == TIDGreaterEqOperator)
+		return true;
+
+	return false;
+}
+
+/*
+ * Check to see if a RestrictInfo is of the form
+ *		CTID = ANY (pseudoconstant_array)
+ * where the CTID Var belongs to relation "rel", and nothing on the
+ * other side of the clause does.
+ */
+static bool
+IsTidEqualAnyClause(PlannerInfo *root, RestrictInfo *rinfo, RelOptInfo *rel)
+{
+	ScalarArrayOpExpr *node;
+	Node	   *arg1,
+			   *arg2;
+
+	/* Must be a ScalarArrayOpExpr */
+	if (!(rinfo->clause && IsA(rinfo->clause, ScalarArrayOpExpr)))
+		return false;
+	node = (ScalarArrayOpExpr *) rinfo->clause;
+
+	/* Operator must be tideq */
+	if (node->opno != TIDEqualOperator)
+		return false;
+	if (!node->useOr)
+		return false;
+	Assert(list_length(node->args) == 2);
+	arg1 = linitial(node->args);
+	arg2 = lsecond(node->args);
+
+	/* CTID must be first argument */
+	if (arg1 && IsA(arg1, Var) &&
+		IsCTIDVar((Var *) arg1, rel))
+	{
+		/* The other argument must be a pseudoconstant */
+		if (bms_is_member(rel->relid, pull_varnos(root, arg2)) ||
+			contain_volatile_functions(arg2))
+			return false;
+
+		return true;			/* success */
+	}
+
+	return false;
+}
+
+/*
+ * Check to see if a RestrictInfo is a CurrentOfExpr referencing "rel".
+ */
+static bool
+IsCurrentOfClause(RestrictInfo *rinfo, RelOptInfo *rel)
+{
+	CurrentOfExpr *node;
+
+	/* Must be a CurrentOfExpr */
+	if (!(rinfo->clause && IsA(rinfo->clause, CurrentOfExpr)))
+		return false;
+	node = (CurrentOfExpr *) rinfo->clause;
+
+	/* If it references this rel, we're good */
+	if (node->cvarno == rel->relid)
+		return true;
+
+	return false;
+}
+
+/*
+ * Extract a set of CTID conditions from the given RestrictInfo
+ *
+ * Returns a List of CTID qual RestrictInfos for the specified rel (with
+ * implicit OR semantics across the list), or NIL if there are no usable
+ * conditions.
+ *
+ * This function considers only base cases; AND/OR combination is handled
+ * below.  Therefore the returned List never has more than one element.
+ * (Using a List may seem a bit weird, but it simplifies the caller.)
+ */
+static List *
+TidQualFromRestrictInfo(PlannerInfo *root, RestrictInfo *rinfo, RelOptInfo *rel)
+{
+	/*
+	 * We may ignore pseudoconstant clauses (they can't contain Vars, so could
+	 * not match anyway).
+	 */
+	if (rinfo->pseudoconstant)
+		return NIL;
+
+	/*
+	 * If clause must wait till after some lower-security-level restriction
+	 * clause, reject it.
+	 */
+	if (!restriction_is_securely_promotable(rinfo, rel))
+		return NIL;
+
+	/*
+	 * Check all base cases.  If we get a match, return the clause.
+	 */
+	if (IsTidEqualClause(rinfo, rel) ||
+		IsTidEqualAnyClause(root, rinfo, rel) ||
+		IsCurrentOfClause(rinfo, rel))
+		return list_make1(rinfo);
+
+	return NIL;
+}
+
+/*
+ * Extract a set of CTID conditions from implicit-AND List of RestrictInfos
+ *
+ * Returns a List of CTID qual RestrictInfos for the specified rel (with
+ * implicit OR semantics across the list), or NIL if there are no usable
+ * equality conditions.
+ *
+ * This function is just concerned with handling AND/OR recursion.
+ */
+static List *
+TidQualFromRestrictInfoList(PlannerInfo *root, List *rlist, RelOptInfo *rel)
+{
+	List	   *rlst = NIL;
+	ListCell   *l;
+
+	foreach(l, rlist)
+	{
+		RestrictInfo *rinfo = lfirst_node(RestrictInfo, l);
+
+		if (restriction_is_or_clause(rinfo))
+		{
+			ListCell   *j;
+
+			/*
+			 * We must be able to extract a CTID condition from every
+			 * sub-clause of an OR, or we can't use it.
+			 */
+			foreach(j, ((BoolExpr *) rinfo->orclause)->args)
+			{
+				Node	   *orarg = (Node *) lfirst(j);
+				List	   *sublist;
+
+				/* OR arguments should be ANDs or sub-RestrictInfos */
+				if (is_andclause(orarg))
+				{
+					List	   *andargs = ((BoolExpr *) orarg)->args;
+
+					/* Recurse in case there are sub-ORs */
+					sublist = TidQualFromRestrictInfoList(root, andargs, rel);
+				}
+				else
+				{
+					RestrictInfo *rinfo = castNode(RestrictInfo, orarg);
+
+					Assert(!restriction_is_or_clause(rinfo));
+					sublist = TidQualFromRestrictInfo(root, rinfo, rel);
+				}
+
+				/*
+				 * If nothing found in this arm, we can't do anything with
+				 * this OR clause.
+				 */
+				if (sublist == NIL)
+				{
+					rlst = NIL; /* forget anything we had */
+					break;		/* out of loop over OR args */
+				}
+
+				/*
+				 * OK, continue constructing implicitly-OR'ed result list.
+				 */
+				rlst = list_concat(rlst, sublist);
+			}
+		}
+		else
+		{
+			/* Not an OR clause, so handle base cases */
+			rlst = TidQualFromRestrictInfo(root, rinfo, rel);
+		}
+
+		/*
+		 * Stop as soon as we find any usable CTID condition.  In theory we
+		 * could get CTID equality conditions from different AND'ed clauses,
+		 * in which case we could try to pick the most efficient one.  In
+		 * practice, such usage seems very unlikely, so we don't bother; we
+		 * just exit as soon as we find the first candidate.
+		 */
+		if (rlst)
+			break;
+	}
+
+	return rlst;
+}
+
+/*
+ * Extract a set of CTID range conditions from implicit-AND List of RestrictInfos
+ *
+ * Returns a List of CTID range qual RestrictInfos for the specified rel
+ * (with implicit AND semantics across the list), or NIL if there are no
+ * usable range conditions or if the rel's table AM does not support TID range
+ * scans.
+ */
+static List *
+TidRangeQualFromRestrictInfoList(List *rlist, RelOptInfo *rel)
+{
+	List	   *rlst = NIL;
+	ListCell   *l;
+
+	if ((rel->amflags & AMFLAG_HAS_TID_RANGE) == 0)
+		return NIL;
+
+	foreach(l, rlist)
+	{
+		RestrictInfo *rinfo = lfirst_node(RestrictInfo, l);
+
+		if (IsTidRangeClause(rinfo, rel))
+			rlst = lappend(rlst, rinfo);
+	}
+
+	return rlst;
+}
+
+/*
+ * Given a list of join clauses involving our rel, create a parameterized
+ * TidPath for each one that is a suitable TidEqual clause.
+ *
+ * In principle we could combine clauses that reference the same outer rels,
+ * but it doesn't seem like such cases would arise often enough to be worth
+ * troubling over.
+ */
+static void
+BuildParameterizedTidPaths(PlannerInfo *root, RelOptInfo *rel, List *clauses)
+{
+	ListCell   *l;
+
+	foreach(l, clauses)
+	{
+		RestrictInfo *rinfo = lfirst_node(RestrictInfo, l);
+		List	   *tidquals;
+		Relids		required_outer;
+
+		/*
+		 * Validate whether each clause is actually usable; we must check this
+		 * even when examining clauses generated from an EquivalenceClass,
+		 * since they might not satisfy the restriction on not having Vars of
+		 * our rel on the other side, or somebody might've built an operator
+		 * class that accepts type "tid" but has other operators in it.
+		 *
+		 * We currently consider only TidEqual join clauses.  In principle we
+		 * might find a suitable ScalarArrayOpExpr in the rel's joininfo list,
+		 * but it seems unlikely to be worth expending the cycles to check.
+		 * And we definitely won't find a CurrentOfExpr here.  Hence, we don't
+		 * use TidQualFromRestrictInfo; but this must match that function
+		 * otherwise.
+		 */
+		if (rinfo->pseudoconstant ||
+			!restriction_is_securely_promotable(rinfo, rel) ||
+			!IsTidEqualClause(rinfo, rel))
+			continue;
+
+		/*
+		 * Check if clause can be moved to this rel; this is probably
+		 * redundant when considering EC-derived clauses, but we must check it
+		 * for "loose" join clauses.
+		 */
+		if (!join_clause_is_movable_to(rinfo, rel))
+			continue;
+
+		/* OK, make list of clauses for this path */
+		tidquals = list_make1(rinfo);
+
+		/* Compute required outer rels for this path */
+		required_outer = bms_union(rinfo->required_relids, rel->lateral_relids);
+		required_outer = bms_del_member(required_outer, rel->relid);
+
+		add_path(rel, (Path *) create_tidscan_path(root, rel, tidquals,
+												   required_outer));
+	}
+}
+
+/*
+ * Test whether an EquivalenceClass member matches our rel's CTID Var.
+ *
+ * This is a callback for use by generate_implied_equalities_for_column.
+ */
+static bool
+ec_member_matches_ctid(PlannerInfo *root, RelOptInfo *rel,
+					   EquivalenceClass *ec, EquivalenceMember *em,
+					   void *arg)
+{
+	if (em->em_expr && IsA(em->em_expr, Var) &&
+		IsCTIDVar((Var *) em->em_expr, rel))
+		return true;
+	return false;
+}
+
+/*
+ * create_tidscan_paths
+ *	  Create paths corresponding to direct TID scans of the given rel.
+ *
+ *	  Candidate paths are added to the rel's pathlist (using add_path).
+ */
+void
+create_tidscan_paths(PlannerInfo *root, RelOptInfo *rel)
+{
+	List	   *tidquals;
+	List	   *tidrangequals;
+
+	/*
+	 * If any suitable quals exist in the rel's baserestrict list, generate a
+	 * plain (unparameterized) TidPath with them.
+	 */
+	tidquals = TidQualFromRestrictInfoList(root, rel->baserestrictinfo, rel);
+
+	if (tidquals != NIL)
+	{
+		/*
+		 * This path uses no join clauses, but it could still have required
+		 * parameterization due to LATERAL refs in its tlist.
+		 */
+		Relids		required_outer = rel->lateral_relids;
+
+		add_path(rel, (Path *) create_tidscan_path(root, rel, tidquals,
+												   required_outer));
+	}
+
+	/*
+	 * If there are range quals in the baserestrict list, generate a
+	 * TidRangePath.
+	 */
+	tidrangequals = TidRangeQualFromRestrictInfoList(rel->baserestrictinfo,
+													 rel);
+
+	if (tidrangequals != NIL)
+	{
+		/*
+		 * This path uses no join clauses, but it could still have required
+		 * parameterization due to LATERAL refs in its tlist.
+		 */
+		Relids		required_outer = rel->lateral_relids;
+
+		add_path(rel, (Path *) create_tidrangescan_path(root, rel,
+														tidrangequals,
+														required_outer));
+	}
+
+	/*
+	 * Try to generate parameterized TidPaths using equality clauses extracted
+	 * from EquivalenceClasses.  (This is important since simple "t1.ctid =
+	 * t2.ctid" clauses will turn into ECs.)
+	 */
+	if (rel->has_eclass_joins)
+	{
+		List	   *clauses;
+
+		/* Generate clauses, skipping any that join to lateral_referencers */
+		clauses = generate_implied_equalities_for_column(root,
+														 rel,
+														 ec_member_matches_ctid,
+														 NULL,
+														 rel->lateral_referencers);
+
+		/* Generate a path for each usable join clause */
+		BuildParameterizedTidPaths(root, rel, clauses);
+	}
+
+	/*
+	 * Also consider parameterized TidPaths using "loose" join quals.  Quals
+	 * of the form "t1.ctid = t2.ctid" would turn into these if they are outer
+	 * join quals, for example.
+	 */
+	BuildParameterizedTidPaths(root, rel, rel->joininfo);
+}