Add infrastructure to support EphemeralNamedRelation references.

A QueryEnvironment concept is added, which allows new types of
objects to be passed into queries from parsing on through
execution.  At this point, the only thing implemented is a
collection of EphemeralNamedRelation objects -- relations which
can be referenced by name in queries, but do not exist in the
catalogs.  The only type of ENR implemented is NamedTuplestore, but
provision is made to add more types fairly easily.

An ENR can carry its own TupleDesc or reference a relation in the
catalogs by relid.

Although these features can be used without SPI, convenience
functions are added to SPI so that ENRs can easily be used by code
run through SPI.

The initial use of all this is going to be transition tables in
AFTER triggers, but that will be added to each PL as a separate
commit.

An incidental effect of this patch is to produce a more informative
error message if an attempt is made to modify the contents of a CTE
from a referencing DML statement.  No tests previously covered that
possibility, so one is added.

Kevin Grittner and Thomas Munro
Reviewed by Heikki Linnakangas, David Fetter, and Thomas Munro
with valuable comments and suggestions from many others

1 files changed, 71 insertions, 0 deletions

diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
index ed06a8de787..2a78595e1f2 100644
--- a/src/backend/optimizer/plan/createplan.c
+++ b/src/backend/optimizer/plan/createplan.c
@@ -139,6 +139,8 @@ static TableFuncScan *create_tablefuncscan_plan(PlannerInfo *root, Path *best_pa
 						  List *tlist, List *scan_clauses);
 static CteScan *create_ctescan_plan(PlannerInfo *root, Path *best_path,
 					List *tlist, List *scan_clauses);
+static NamedTuplestoreScan *create_namedtuplestorescan_plan(PlannerInfo *root,
+					Path *best_path, List *tlist, List *scan_clauses);
 static WorkTableScan *create_worktablescan_plan(PlannerInfo *root, Path *best_path,
 						  List *tlist, List *scan_clauses);
 static ForeignScan *create_foreignscan_plan(PlannerInfo *root, ForeignPath *best_path,
@@ -197,6 +199,8 @@ static TableFuncScan *make_tablefuncscan(List *qptlist, List *qpqual,
 				   Index scanrelid, TableFunc *tablefunc);
 static CteScan *make_ctescan(List *qptlist, List *qpqual,
 			 Index scanrelid, int ctePlanId, int cteParam);
+static NamedTuplestoreScan *make_namedtuplestorescan(List *qptlist, List *qpqual,
+			 Index scanrelid, char *enrname);
 static WorkTableScan *make_worktablescan(List *qptlist, List *qpqual,
 				   Index scanrelid, int wtParam);
 static Append *make_append(List *appendplans, List *tlist, List *partitioned_rels);
@@ -366,6 +370,7 @@ create_plan_recurse(PlannerInfo *root, Path *best_path, int flags)
 		case T_ValuesScan:
 		case T_CteScan:
 		case T_WorkTableScan:
+		case T_NamedTuplestoreScan:
 		case T_ForeignScan:
 		case T_CustomScan:
 			plan = create_scan_plan(root, best_path, flags);
@@ -668,6 +673,13 @@ create_scan_plan(PlannerInfo *root, Path *best_path, int flags)
 												scan_clauses);
 			break;
 
+		case T_NamedTuplestoreScan:
+			plan = (Plan *) create_namedtuplestorescan_plan(root,
+															best_path,
+															tlist,
+															scan_clauses);
+			break;
+
 		case T_WorkTableScan:
 			plan = (Plan *) create_worktablescan_plan(root,
 													  best_path,
@@ -3286,6 +3298,45 @@ create_ctescan_plan(PlannerInfo *root, Path *best_path,
 }
 
 /*
+ * create_namedtuplestorescan_plan
+ *	 Returns a tuplestorescan plan for the base relation scanned by
+ *	'best_path' with restriction clauses 'scan_clauses' and targetlist
+ *	'tlist'.
+ */
+static NamedTuplestoreScan *
+create_namedtuplestorescan_plan(PlannerInfo *root, Path *best_path,
+								List *tlist, List *scan_clauses)
+{
+	NamedTuplestoreScan *scan_plan;
+	Index		scan_relid = best_path->parent->relid;
+	RangeTblEntry *rte;
+
+	Assert(scan_relid > 0);
+	rte = planner_rt_fetch(scan_relid, root);
+	Assert(rte->rtekind == RTE_NAMEDTUPLESTORE);
+
+	/* Sort clauses into best execution order */
+	scan_clauses = order_qual_clauses(root, scan_clauses);
+
+	/* Reduce RestrictInfo list to bare expressions; ignore pseudoconstants */
+	scan_clauses = extract_actual_clauses(scan_clauses, false);
+
+	/* Replace any outer-relation variables with nestloop params */
+	if (best_path->param_info)
+	{
+		scan_clauses = (List *)
+			replace_nestloop_params(root, (Node *) scan_clauses);
+	}
+
+	scan_plan = make_namedtuplestorescan(tlist, scan_clauses, scan_relid,
+										 rte->enrname);
+
+	copy_generic_path_info(&scan_plan->scan.plan, best_path);
+
+	return scan_plan;
+}
+
+/*
  * create_worktablescan_plan
  *	 Returns a worktablescan plan for the base relation scanned by 'best_path'
  *	 with restriction clauses 'scan_clauses' and targetlist 'tlist'.
@@ -5120,6 +5171,26 @@ make_ctescan(List *qptlist,
 	return node;
 }
 
+static NamedTuplestoreScan *
+make_namedtuplestorescan(List *qptlist,
+						 List *qpqual,
+						 Index scanrelid,
+						 char *enrname)
+{
+	NamedTuplestoreScan *node = makeNode(NamedTuplestoreScan);
+	Plan	   *plan = &node->scan.plan;
+
+	/* cost should be inserted by caller */
+	plan->targetlist = qptlist;
+	plan->qual = qpqual;
+	plan->lefttree = NULL;
+	plan->righttree = NULL;
+	node->scan.scanrelid = scanrelid;
+	node->enrname = enrname;
+
+	return node;
+}
+
 static WorkTableScan *
 make_worktablescan(List *qptlist,
 				   List *qpqual,