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, 140 insertions, 3 deletions

diff --git a/src/backend/parser/parse_relation.c b/src/backend/parser/parse_relation.c
index 2c19e0cbf58..7db13f37f72 100644
--- a/src/backend/parser/parse_relation.c
+++ b/src/backend/parser/parse_relation.c
@@ -25,6 +25,7 @@
 #include "nodes/makefuncs.h"
 #include "nodes/nodeFuncs.h"
 #include "parser/parsetree.h"
+#include "parser/parse_enr.h"
 #include "parser/parse_relation.h"
 #include "parser/parse_type.h"
 #include "utils/builtins.h"
@@ -282,6 +283,16 @@ isFutureCTE(ParseState *pstate, const char *refname)
 }
 
 /*
+ * Search the query's ephemeral named relation namespace for a relation
+ * matching the given unqualified refname.
+ */
+bool
+scanNameSpaceForENR(ParseState *pstate, const char *refname)
+{
+	return name_matches_visible_ENR(pstate, refname);
+}
+
+/*
  * searchRangeTableForRel
  *	  See if any RangeTblEntry could possibly match the RangeVar.
  *	  If so, return a pointer to the RangeTblEntry; else return NULL.
@@ -302,6 +313,7 @@ searchRangeTableForRel(ParseState *pstate, RangeVar *relation)
 	const char *refname = relation->relname;
 	Oid			relId = InvalidOid;
 	CommonTableExpr *cte = NULL;
+	bool		isenr = false;
 	Index		ctelevelsup = 0;
 	Index		levelsup;
 
@@ -318,11 +330,16 @@ searchRangeTableForRel(ParseState *pstate, RangeVar *relation)
 	 * unlocked.
 	 */
 	if (!relation->schemaname)
+	{
 		cte = scanNameSpaceForCTE(pstate, refname, &ctelevelsup);
-	if (!cte)
+		if (!cte)
+			isenr = scanNameSpaceForENR(pstate, refname);
+	}
+
+	if (!cte && !isenr)
 		relId = RangeVarGetRelid(relation, NoLock, true);
 
-	/* Now look for RTEs matching either the relation/CTE or the alias */
+	/* Now look for RTEs matching either the relation/CTE/ENR or the alias */
 	for (levelsup = 0;
 		 pstate != NULL;
 		 pstate = pstate->parentParseState, levelsup++)
@@ -342,6 +359,10 @@ searchRangeTableForRel(ParseState *pstate, RangeVar *relation)
 				rte->ctelevelsup + levelsup == ctelevelsup &&
 				strcmp(rte->ctename, refname) == 0)
 				return rte;
+			if (rte->rtekind == RTE_NAMEDTUPLESTORE &&
+				isenr &&
+				strcmp(rte->enrname, refname) == 0)
+				return rte;
 			if (strcmp(rte->eref->aliasname, refname) == 0)
 				return rte;
 		}
@@ -1139,12 +1160,17 @@ parserOpenTable(ParseState *pstate, const RangeVar *relation, int lockmode)
 		else
 		{
 			/*
+			 * An unqualified name might be a named ephemeral relation.
+			 */
+			if (get_visible_ENR_metadata(pstate->p_queryEnv, relation->relname))
+				rel = NULL;
+			/*
 			 * An unqualified name might have been meant as a reference to
 			 * some not-yet-in-scope CTE.  The bare "does not exist" message
 			 * has proven remarkably unhelpful for figuring out such problems,
 			 * so we take pains to offer a specific hint.
 			 */
-			if (isFutureCTE(pstate, relation->relname))
+			else if (isFutureCTE(pstate, relation->relname))
 				ereport(ERROR,
 						(errcode(ERRCODE_UNDEFINED_TABLE),
 						 errmsg("relation \"%s\" does not exist",
@@ -1940,6 +1966,102 @@ addRangeTableEntryForCTE(ParseState *pstate,
 	return rte;
 }
 
+/*
+ * Add an entry for an ephemeral named relation reference to the pstate's
+ * range table (p_rtable).
+ *
+ * It is expected that the RangeVar, which up until now is only known to be an
+ * ephemeral named relation, will (in conjunction with the QueryEnvironment in
+ * the ParseState), create a RangeTblEntry for a specific *kind* of ephemeral
+ * named relation, based on enrtype.
+ *
+ * This is much like addRangeTableEntry() except that it makes an RTE for an
+ * ephemeral named relation.
+ */
+RangeTblEntry *
+addRangeTableEntryForENR(ParseState *pstate,
+						 RangeVar *rv,
+						 bool inFromCl)
+{
+	RangeTblEntry *rte = makeNode(RangeTblEntry);
+	Alias	   *alias = rv->alias;
+	char	   *refname = alias ? alias->aliasname : rv->relname;
+	EphemeralNamedRelationMetadata enrmd =
+	  get_visible_ENR(pstate, rv->relname);
+	TupleDesc	tupdesc;
+	int			attno;
+
+	Assert(enrmd != NULL);
+
+	switch (enrmd->enrtype)
+	{
+		case ENR_NAMED_TUPLESTORE:
+			rte->rtekind = RTE_NAMEDTUPLESTORE;
+			break;
+
+		default:
+			elog(ERROR, "unexpected enrtype of %i", enrmd->enrtype);
+			return NULL;  /* for fussy compilers */
+	}
+
+	/*
+	 * Record dependency on a relation.  This allows plans to be invalidated
+	 * if they access transition tables linked to a table that is altered.
+	 */
+	rte->relid = enrmd->reliddesc;
+
+	/*
+	 * Build the list of effective column names using user-supplied aliases
+	 * and/or actual column names.  Also build the cannibalized fields.
+	 */
+	tupdesc = ENRMetadataGetTupDesc(enrmd);
+	rte->eref = makeAlias(refname, NIL);
+	buildRelationAliases(tupdesc, alias, rte->eref);
+	rte->enrname = enrmd->name;
+	rte->enrtuples = enrmd->enrtuples;
+	rte->coltypes = NIL;
+	rte->coltypmods = NIL;
+	rte->colcollations = NIL;
+	for (attno = 1; attno <= tupdesc->natts; ++attno)
+	{
+		if (tupdesc->attrs[attno - 1]->atttypid == InvalidOid &&
+			!(tupdesc->attrs[attno - 1]->attisdropped))
+			elog(ERROR, "atttypid was invalid for column which has not been dropped from \"%s\"",
+				 rv->relname);
+		rte->coltypes =
+			lappend_oid(rte->coltypes,
+						tupdesc->attrs[attno - 1]->atttypid);
+		rte->coltypmods =
+			lappend_int(rte->coltypmods,
+						tupdesc->attrs[attno - 1]->atttypmod);
+		rte->colcollations =
+			lappend_oid(rte->colcollations,
+						tupdesc->attrs[attno - 1]->attcollation);
+	}
+
+	/*
+	 * Set flags and access permissions.
+	 *
+	 * ENRs are never checked for access rights.
+	 */
+	rte->lateral = false;
+	rte->inh = false;			/* never true for ENRs */
+	rte->inFromCl = inFromCl;
+
+	rte->requiredPerms = 0;
+	rte->checkAsUser = InvalidOid;
+	rte->selectedCols = NULL;
+
+	/*
+	 * Add completed RTE to pstate's range table list, but not to join list
+	 * nor namespace --- caller must do that if appropriate.
+	 */
+	if (pstate != NULL)
+		pstate->p_rtable = lappend(pstate->p_rtable, rte);
+
+	return rte;
+}
+
 
 /*
  * Has the specified refname been selected FOR UPDATE/FOR SHARE?
@@ -2292,6 +2414,7 @@ expandRTE(RangeTblEntry *rte, int rtindex, int sublevels_up,
 		case RTE_TABLEFUNC:
 		case RTE_VALUES:
 		case RTE_CTE:
+		case RTE_NAMEDTUPLESTORE:
 			{
 				/* Tablefunc, Values or CTE RTE */
 				ListCell   *aliasp_item = list_head(rte->eref->colnames);
@@ -2705,6 +2828,7 @@ get_rte_attribute_type(RangeTblEntry *rte, AttrNumber attnum,
 		case RTE_TABLEFUNC:
 		case RTE_VALUES:
 		case RTE_CTE:
+		case RTE_NAMEDTUPLESTORE:
 			{
 				/*
 				 * tablefunc, VALUES or CTE RTE --- get type info from lists
@@ -2762,6 +2886,19 @@ get_rte_attribute_is_dropped(RangeTblEntry *rte, AttrNumber attnum)
 			 */
 			result = false;
 			break;
+		case RTE_NAMEDTUPLESTORE:
+			{
+				Assert(rte->enrname);
+
+				/*
+				 * We checked when we loaded ctecoltypes for the tuplestore
+				 * that InvalidOid was only used for dropped columns, so it is
+				 * safe to count on that here.
+				 */
+				result =
+					(list_nth(rte->coltypes, attnum - 1) != InvalidOid);
+			}
+			break;
 		case RTE_JOIN:
 			{
 				/*