Restructure SELECT INTO's parsetree representation into CreateTableAsStmt.

Making this operation look like a utility statement seems generally a good
idea, and particularly so in light of the desire to provide command
triggers for utility statements.  The original choice of representing it as
SELECT with an IntoClause appendage had metastasized into rather a lot of
places, unfortunately, so that this patch is a great deal more complicated
than one might at first expect.

In particular, keeping EXPLAIN working for SELECT INTO and CREATE TABLE AS
subcommands required restructuring some EXPLAIN-related APIs.  Add-on code
that calls ExplainOnePlan or ExplainOneUtility, or uses
ExplainOneQuery_hook, will need adjustment.

Also, the cases PREPARE ... SELECT INTO and CREATE RULE ... SELECT INTO,
which formerly were accepted though undocumented, are no longer accepted.
The PREPARE case can be replaced with use of CREATE TABLE AS EXECUTE.
The CREATE RULE case doesn't seem to have much real-world use (since the
rule would work only once before failing with "table already exists"),
so we'll not bother with that one.

Both SELECT INTO and CREATE TABLE AS still return a command tag of
"SELECT nnnn".  There was some discussion of returning "CREATE TABLE nnnn",
but for the moment backwards compatibility wins the day.

Andres Freund and Tom Lane

1 files changed, 12 insertions, 18 deletions

diff --git a/src/backend/utils/cache/plancache.c b/src/backend/utils/cache/plancache.c
index 7e66645b2b6..6292f8dc6c9 100644
--- a/src/backend/utils/cache/plancache.c
+++ b/src/backend/utils/cache/plancache.c
@@ -1232,20 +1232,16 @@ AcquireExecutorLocks(List *stmt_list, bool acquire)
 		if (!IsA(plannedstmt, PlannedStmt))
 		{
 			/*
-			 * Ignore utility statements, except EXPLAIN which contains a
-			 * parsed-but-not-planned query.  Note: it's okay to use
+			 * Ignore utility statements, except those (such as EXPLAIN) that
+			 * contain a parsed-but-not-planned query.  Note: it's okay to use
 			 * ScanQueryForLocks, even though the query hasn't been through
 			 * rule rewriting, because rewriting doesn't change the query
 			 * representation.
 			 */
-			if (IsA(plannedstmt, ExplainStmt))
-			{
-				Query	   *query;
+			Query	   *query = UtilityContainsQuery((Node *) plannedstmt);
 
-				query = (Query *) ((ExplainStmt *) plannedstmt)->query;
-				Assert(IsA(query, Query));
+			if (query)
 				ScanQueryForLocks(query, acquire);
-			}
 			continue;
 		}
 
@@ -1304,13 +1300,10 @@ AcquirePlannerLocks(List *stmt_list, bool acquire)
 
 		if (query->commandType == CMD_UTILITY)
 		{
-			/* Ignore utility statements, except EXPLAIN */
-			if (IsA(query->utilityStmt, ExplainStmt))
-			{
-				query = (Query *) ((ExplainStmt *) query->utilityStmt)->query;
-				Assert(IsA(query, Query));
+			/* Ignore utility statements, unless they contain a Query */
+			query = UtilityContainsQuery(query->utilityStmt);
+			if (query)
 				ScanQueryForLocks(query, acquire);
-			}
 			continue;
 		}
 
@@ -1648,9 +1641,9 @@ ResetPlanCache(void)
 		 * aborted transactions when we can't revalidate them (cf bug #5269).
 		 * In general there is no point in invalidating utility statements
 		 * since they have no plans anyway.  So invalidate it only if it
-		 * contains at least one non-utility statement.  (EXPLAIN counts as a
-		 * non-utility statement, though, since it contains an analyzed query
-		 * that might have dependencies.)
+		 * contains at least one non-utility statement, or contains a utility
+		 * statement that contains a pre-analyzed query (which could have
+		 * dependencies.)
 		 */
 		foreach(lc, plansource->query_list)
 		{
@@ -1658,12 +1651,13 @@ ResetPlanCache(void)
 
 			Assert(IsA(query, Query));
 			if (query->commandType != CMD_UTILITY ||
-				IsA(query->utilityStmt, ExplainStmt))
+				UtilityContainsQuery(query->utilityStmt))
 			{
 				/* non-utility statement, so invalidate */
 				plansource->is_valid = false;
 				if (plansource->gplan)
 					plansource->gplan->is_valid = false;
+				/* no need to look further */
 				break;
 			}
 		}