Add a materialized view relations.

A materialized view has a rule just like a view and a heap and
other physical properties like a table.  The rule is only used to
populate the table, references in queries refer to the
materialized data.

This is a minimal implementation, but should still be useful in
many cases.  Currently data is only populated "on demand" by the
CREATE MATERIALIZED VIEW and REFRESH MATERIALIZED VIEW statements.
It is expected that future releases will add incremental updates
with various timings, and that a more refined concept of defining
what is "fresh" data will be developed.  At some point it may even
be possible to have queries use a materialized in place of
references to underlying tables, but that requires the other
above-mentioned features to be working first.

Much of the documentation work by Robert Haas.
Review by Noah Misch, Thom Brown, Robert Haas, Marko Tiikkaja
Security review by KaiGai Kohei, with a decision on how best to
implement sepgsql still pending.

1 files changed, 15 insertions, 20 deletions

diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index fbad0d027ae..989b52da9d4 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -47,7 +47,7 @@ explain_get_index_name_hook_type explain_get_index_name_hook = NULL;
 #define X_NOWHITESPACE 4
 
 static void ExplainOneQuery(Query *query, IntoClause *into, ExplainState *es,
-				const char *queryString, ParamListInfo params);
+				const char *queryString, DestReceiver *dest, ParamListInfo params);
 static void report_triggers(ResultRelInfo *rInfo, bool show_relname,
 				ExplainState *es);
 static double elapsed_time(instr_time *starttime);
@@ -218,7 +218,7 @@ ExplainQuery(ExplainStmt *stmt, const char *queryString,
 		foreach(l, rewritten)
 		{
 			ExplainOneQuery((Query *) lfirst(l), NULL, &es,
-							queryString, params);
+							queryString, None_Receiver, params);
 
 			/* Separate plans with an appropriate separator */
 			if (lnext(l) != NULL)
@@ -299,7 +299,8 @@ ExplainResultDesc(ExplainStmt *stmt)
  */
 static void
 ExplainOneQuery(Query *query, IntoClause *into, ExplainState *es,
-				const char *queryString, ParamListInfo params)
+				const char *queryString, DestReceiver *dest,
+				ParamListInfo params)
 {
 	/* planner will not cope with utility statements */
 	if (query->commandType == CMD_UTILITY)
@@ -319,7 +320,7 @@ ExplainOneQuery(Query *query, IntoClause *into, ExplainState *es,
 		plan = pg_plan_query(query, 0, params);
 
 		/* run it (if needed) and produce output */
-		ExplainOnePlan(plan, into, es, queryString, params);
+		ExplainOnePlan(plan, into, es, queryString, dest, params);
 	}
 }
 
@@ -343,19 +344,23 @@ ExplainOneUtility(Node *utilityStmt, IntoClause *into, ExplainState *es,
 
 	if (IsA(utilityStmt, CreateTableAsStmt))
 	{
+		DestReceiver	*dest;
+
 		/*
 		 * We have to rewrite the contained SELECT and then pass it back to
 		 * ExplainOneQuery.  It's probably not really necessary to copy the
 		 * contained parsetree another time, but let's be safe.
 		 */
 		CreateTableAsStmt *ctas = (CreateTableAsStmt *) utilityStmt;
-		List	   *rewritten;
+		Query	   *query = (Query *) ctas->query;
+
+		dest = CreateIntoRelDestReceiver(into);
 
 		Assert(IsA(ctas->query, Query));
-		rewritten = QueryRewrite((Query *) copyObject(ctas->query));
-		Assert(list_length(rewritten) == 1);
-		ExplainOneQuery((Query *) linitial(rewritten), ctas->into, es,
-						queryString, params);
+
+		query = SetupForCreateTableAs(query, ctas->into, queryString, params, dest);
+
+		ExplainOneQuery(query, ctas->into, es, queryString, dest, params);
 	}
 	else if (IsA(utilityStmt, ExecuteStmt))
 		ExplainExecuteQuery((ExecuteStmt *) utilityStmt, into, es,
@@ -396,9 +401,8 @@ ExplainOneUtility(Node *utilityStmt, IntoClause *into, ExplainState *es,
  */
 void
 ExplainOnePlan(PlannedStmt *plannedstmt, IntoClause *into, ExplainState *es,
-			   const char *queryString, ParamListInfo params)
+			   const char *queryString, DestReceiver *dest, ParamListInfo params)
 {
-	DestReceiver *dest;
 	QueryDesc  *queryDesc;
 	instr_time	starttime;
 	double		totaltime = 0;
@@ -422,15 +426,6 @@ ExplainOnePlan(PlannedStmt *plannedstmt, IntoClause *into, ExplainState *es,
 	PushCopiedSnapshot(GetActiveSnapshot());
 	UpdateActiveSnapshotCommandId();
 
-	/*
-	 * Normally we discard the query's output, but if explaining CREATE TABLE
-	 * AS, we'd better use the appropriate tuple receiver.
-	 */
-	if (into)
-		dest = CreateIntoRelDestReceiver(into);
-	else
-		dest = None_Receiver;
-
 	/* Create a QueryDesc for the query */
 	queryDesc = CreateQueryDesc(plannedstmt, queryString,
 								GetActiveSnapshot(), InvalidSnapshot,