setrefs.c

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/*-------------------------------------------------------------------------
 *
 * setrefs.c
 *	  Post-processing of a completed plan tree: fix references to subplan
 *	  vars, compute regproc values for operators, etc
 *
 * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $PostgreSQL: pgsql/src/backend/optimizer/plan/setrefs.c,v 1.141.2.1 2008/06/17 14:51:38 tgl Exp $
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "catalog/pg_type.h"
#include "nodes/makefuncs.h"
#include "optimizer/clauses.h"
#include "optimizer/planmain.h"
#include "optimizer/tlist.h"
#include "parser/parse_expr.h"
#include "parser/parsetree.h"
#include "utils/lsyscache.h"


typedef struct
{
	Index		varno;			/* RT index of Var */
	AttrNumber	varattno;		/* attr number of Var */
	AttrNumber	resno;			/* TLE position of Var */
} tlist_vinfo;

typedef struct
{
	List	   *tlist;			/* underlying target list */
	int			num_vars;		/* number of plain Var tlist entries */
	bool		has_non_vars;	/* are there non-plain-Var entries? */
	/* array of num_vars entries: */
	tlist_vinfo vars[1];		/* VARIABLE LENGTH ARRAY */
} indexed_tlist;				/* VARIABLE LENGTH STRUCT */

typedef struct
{
	PlannerGlobal *glob;
	int			rtoffset;
} fix_scan_expr_context;

typedef struct
{
	PlannerGlobal *glob;
	indexed_tlist *outer_itlist;
	indexed_tlist *inner_itlist;
	Index		acceptable_rel;
	int			rtoffset;
} fix_join_expr_context;

typedef struct
{
	PlannerGlobal *glob;
	indexed_tlist *subplan_itlist;
	int			rtoffset;
} fix_upper_expr_context;

/*
 * Check if a Const node is a regclass value.  We accept plain OID too,
 * since a regclass Const will get folded to that type if it's an argument
 * to oideq or similar operators.  (This might result in some extraneous
 * values in a plan's list of relation dependencies, but the worst result
 * would be occasional useless replans.)
 */
#define ISREGCLASSCONST(con) \
	(((con)->consttype == REGCLASSOID || (con)->consttype == OIDOID) && \
	 !(con)->constisnull)

#define fix_scan_list(glob, lst, rtoffset) \
	((List *) fix_scan_expr(glob, (Node *) (lst), rtoffset))

static Plan *set_plan_refs(PlannerGlobal *glob, Plan *plan, int rtoffset);
static Plan *set_subqueryscan_references(PlannerGlobal *glob,
							SubqueryScan *plan,
							int rtoffset);
static bool trivial_subqueryscan(SubqueryScan *plan);
static Node *fix_scan_expr(PlannerGlobal *glob, Node *node, int rtoffset);
static Node *fix_scan_expr_mutator(Node *node, fix_scan_expr_context *context);
static bool fix_scan_expr_walker(Node *node, fix_scan_expr_context *context);
static void set_join_references(PlannerGlobal *glob, Join *join, int rtoffset);
static void set_inner_join_references(PlannerGlobal *glob, Plan *inner_plan,
						  indexed_tlist *outer_itlist);
static void set_upper_references(PlannerGlobal *glob, Plan *plan, int rtoffset);
static void set_dummy_tlist_references(Plan *plan, int rtoffset);
static indexed_tlist *build_tlist_index(List *tlist);
static Var *search_indexed_tlist_for_var(Var *var,
							 indexed_tlist *itlist,
							 Index newvarno,
							 int rtoffset);
static Var *search_indexed_tlist_for_non_var(Node *node,
								 indexed_tlist *itlist,
								 Index newvarno);
static List *fix_join_expr(PlannerGlobal *glob,
			  List *clauses,
			  indexed_tlist *outer_itlist,
			  indexed_tlist *inner_itlist,
			  Index acceptable_rel, int rtoffset);
static Node *fix_join_expr_mutator(Node *node,
					  fix_join_expr_context *context);
static Node *fix_upper_expr(PlannerGlobal *glob,
			   Node *node,
			   indexed_tlist *subplan_itlist,
			   int rtoffset);
static Node *fix_upper_expr_mutator(Node *node,
					   fix_upper_expr_context *context);
static bool fix_opfuncids_walker(Node *node, void *context);


/*****************************************************************************
 *
 *		SUBPLAN REFERENCES
 *
 *****************************************************************************/

/*
 * set_plan_references
 *
 * This is the final processing pass of the planner/optimizer.	The plan
 * tree is complete; we just have to adjust some representational details
 * for the convenience of the executor:
 *
 * 1. We flatten the various subquery rangetables into a single list, and
 * zero out RangeTblEntry fields that are not useful to the executor.
 *
 * 2. We adjust Vars in scan nodes to be consistent with the flat rangetable.
 *
 * 3. We adjust Vars in upper plan nodes to refer to the outputs of their
 * subplans.
 *
 * 4. We compute regproc OIDs for operators (ie, we look up the function
 * that implements each op).
 *
 * 5. We create a list of OIDs of relations that the plan depends on.
 * This will be used by plancache.c to drive invalidation of cached plans.
 * (Someday we might want to generalize this to include other types of
 * objects, but for now tracking relations seems to solve most problems.)
 *
 * We also perform one final optimization step, which is to delete
 * SubqueryScan plan nodes that aren't doing anything useful (ie, have
 * no qual and a no-op targetlist).  The reason for doing this last is that
 * it can't readily be done before set_plan_references, because it would
 * break set_upper_references: the Vars in the subquery's top tlist
 * wouldn't match up with the Vars in the outer plan tree.  The SubqueryScan
 * serves a necessary function as a buffer between outer query and subquery
 * variable numbering ... but after we've flattened the rangetable this is
 * no longer a problem, since then there's only one rtindex namespace.
 *
 * set_plan_references recursively traverses the whole plan tree.
 *
 * Inputs:
 *	glob: global data for planner run
 *	plan: the topmost node of the plan
 *	rtable: the rangetable for the current subquery
 *
 * The return value is normally the same Plan node passed in, but can be
 * different when the passed-in Plan is a SubqueryScan we decide isn't needed.
 *
 * The flattened rangetable entries are appended to glob->finalrtable, and
 * the list of relation OIDs is appended to glob->relationOids.
 *
 * Notice that we modify Plan nodes in-place, but use expression_tree_mutator
 * to process targetlist and qual expressions.	We can assume that the Plan
 * nodes were just built by the planner and are not multiply referenced, but
 * it's not so safe to assume that for expression tree nodes.
 */
Plan *
set_plan_references(PlannerGlobal *glob, Plan *plan, List *rtable)
{
	int			rtoffset = list_length(glob->finalrtable);
	ListCell   *lc;

	/*
	 * In the flat rangetable, we zero out substructure pointers that are not
	 * needed by the executor; this reduces the storage space and copying cost
	 * for cached plans.  We keep only the alias and eref Alias fields, which
	 * are needed by EXPLAIN.
	 */
	foreach(lc, rtable)
	{
		RangeTblEntry *rte = (RangeTblEntry *) lfirst(lc);
		RangeTblEntry *newrte;

		/* flat copy to duplicate all the scalar fields */
		newrte = (RangeTblEntry *) palloc(sizeof(RangeTblEntry));
		memcpy(newrte, rte, sizeof(RangeTblEntry));

		/* zap unneeded sub-structure */
		newrte->subquery = NULL;
		newrte->funcexpr = NULL;
		newrte->funccoltypes = NIL;
		newrte->funccoltypmods = NIL;
		newrte->values_lists = NIL;
		newrte->joinaliasvars = NIL;

		glob->finalrtable = lappend(glob->finalrtable, newrte);

		/*
		 * If it's a plain relation RTE, add the table to relationOids.
		 *
		 * We do this even though the RTE might be unreferenced in the plan
		 * tree; this would correspond to cases such as views that were
		 * expanded, child tables that were eliminated by constraint
		 * exclusion, etc.	Schema invalidation on such a rel must still force
		 * rebuilding of the plan.
		 *
		 * Note we don't bother to avoid duplicate list entries.  We could,
		 * but it would probably cost more cycles than it would save.
		 */
		if (newrte->rtekind == RTE_RELATION)
			glob->relationOids = lappend_oid(glob->relationOids,
											 newrte->relid);
	}

	/* Now fix the Plan tree */
	return set_plan_refs(glob, plan, rtoffset);
}

/*
 * set_plan_refs: recurse through the Plan nodes of a single subquery level
 */
static Plan *
set_plan_refs(PlannerGlobal *glob, Plan *plan, int rtoffset)
{
	ListCell   *l;

	if (plan == NULL)
		return NULL;

	/*
	 * Plan-type-specific fixes
	 */
	switch (nodeTag(plan))
	{
		case T_SeqScan:
			{
				SeqScan    *splan = (SeqScan *) plan;

				splan->scanrelid += rtoffset;
				splan->plan.targetlist =
					fix_scan_list(glob, splan->plan.targetlist, rtoffset);
				splan->plan.qual =
					fix_scan_list(glob, splan->plan.qual, rtoffset);
			}
			break;
		case T_IndexScan:
			{
				IndexScan  *splan = (IndexScan *) plan;

				splan->scan.scanrelid += rtoffset;
				splan->scan.plan.targetlist =
					fix_scan_list(glob, splan->scan.plan.targetlist, rtoffset);
				splan->scan.plan.qual =
					fix_scan_list(glob, splan->scan.plan.qual, rtoffset);
				splan->indexqual =
					fix_scan_list(glob, splan->indexqual, rtoffset);
				splan->indexqualorig =
					fix_scan_list(glob, splan->indexqualorig, rtoffset);
			}
			break;
		case T_BitmapIndexScan:
			{
				BitmapIndexScan *splan = (BitmapIndexScan *) plan;

				splan->scan.scanrelid += rtoffset;
				/* no need to fix targetlist and qual */
				Assert(splan->scan.plan.targetlist == NIL);
				Assert(splan->scan.plan.qual == NIL);
				splan->indexqual =
					fix_scan_list(glob, splan->indexqual, rtoffset);
				splan->indexqualorig =
					fix_scan_list(glob, splan->indexqualorig, rtoffset);
			}
			break;
		case T_BitmapHeapScan:
			{
				BitmapHeapScan *splan = (BitmapHeapScan *) plan;

				splan->scan.scanrelid += rtoffset;
				splan->scan.plan.targetlist =
					fix_scan_list(glob, splan->scan.plan.targetlist, rtoffset);
				splan->scan.plan.qual =
					fix_scan_list(glob, splan->scan.plan.qual, rtoffset);
				splan->bitmapqualorig =
					fix_scan_list(glob, splan->bitmapqualorig, rtoffset);
			}
			break;
		case T_TidScan:
			{
				TidScan    *splan = (TidScan *) plan;

				splan->scan.scanrelid += rtoffset;
				splan->scan.plan.targetlist =
					fix_scan_list(glob, splan->scan.plan.targetlist, rtoffset);
				splan->scan.plan.qual =
					fix_scan_list(glob, splan->scan.plan.qual, rtoffset);
				splan->tidquals =
					fix_scan_list(glob, splan->tidquals, rtoffset);
			}
			break;
		case T_SubqueryScan:
			/* Needs special treatment, see comments below */
			return set_subqueryscan_references(glob,
											   (SubqueryScan *) plan,
											   rtoffset);
		case T_FunctionScan:
			{
				FunctionScan *splan = (FunctionScan *) plan;

				splan->scan.scanrelid += rtoffset;
				splan->scan.plan.targetlist =
					fix_scan_list(glob, splan->scan.plan.targetlist, rtoffset);
				splan->scan.plan.qual =
					fix_scan_list(glob, splan->scan.plan.qual, rtoffset);
				splan->funcexpr =
					fix_scan_expr(glob, splan->funcexpr, rtoffset);
			}
			break;
		case T_ValuesScan:
			{
				ValuesScan *splan = (ValuesScan *) plan;

				splan->scan.scanrelid += rtoffset;
				splan->scan.plan.targetlist =
					fix_scan_list(glob, splan->scan.plan.targetlist, rtoffset);
				splan->scan.plan.qual =
					fix_scan_list(glob, splan->scan.plan.qual, rtoffset);
				splan->values_lists =
					fix_scan_list(glob, splan->values_lists, rtoffset);
			}
			break;

		case T_NestLoop:
		case T_MergeJoin:
		case T_HashJoin:
			set_join_references(glob, (Join *) plan, rtoffset);
			break;

		case T_Hash:
		case T_Material:
		case T_Sort:
		case T_Unique:
		case T_SetOp:

			/*
			 * These plan types don't actually bother to evaluate their
			 * targetlists, because they just return their unmodified input
			 * tuples.	Even though the targetlist won't be used by the
			 * executor, we fix it up for possible use by EXPLAIN (not to
			 * mention ease of debugging --- wrong varnos are very confusing).
			 */
			set_dummy_tlist_references(plan, rtoffset);

			/*
			 * Since these plan types don't check quals either, we should not
			 * find any qual expression attached to them.
			 */
			Assert(plan->qual == NIL);
			break;
		case T_Limit:
			{
				Limit	   *splan = (Limit *) plan;

				/*
				 * Like the plan types above, Limit doesn't evaluate its tlist
				 * or quals.  It does have live expressions for limit/offset,
				 * however; and those cannot contain subplan variable refs, so
				 * fix_scan_expr works for them.
				 */
				set_dummy_tlist_references(plan, rtoffset);
				Assert(splan->plan.qual == NIL);

				splan->limitOffset =
					fix_scan_expr(glob, splan->limitOffset, rtoffset);
				splan->limitCount =
					fix_scan_expr(glob, splan->limitCount, rtoffset);
			}
			break;
		case T_Agg:
		case T_Group:
			set_upper_references(glob, plan, rtoffset);
			break;
		case T_Result:
			{
				Result	   *splan = (Result *) plan;

				/*
				 * Result may or may not have a subplan; if not, it's more
				 * like a scan node than an upper node.
				 */
				if (splan->plan.lefttree != NULL)
					set_upper_references(glob, plan, rtoffset);
				else
				{
					splan->plan.targetlist =
						fix_scan_list(glob, splan->plan.targetlist, rtoffset);
					splan->plan.qual =
						fix_scan_list(glob, splan->plan.qual, rtoffset);
				}
				/* resconstantqual can't contain any subplan variable refs */