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, 10 insertions, 6 deletions

diff --git a/src/backend/commands/view.c b/src/backend/commands/view.c
index 99fb7dbb8f4..c887961bc97 100644
--- a/src/backend/commands/view.c
+++ b/src/backend/commands/view.c
@@ -439,9 +439,17 @@ DefineView(ViewStmt *stmt, const char *queryString)
 
 	/*
 	 * The grammar should ensure that the result is a single SELECT Query.
+	 * However, it doesn't forbid SELECT INTO, so we have to check for that.
 	 */
-	if (!IsA(viewParse, Query) ||
-		viewParse->commandType != CMD_SELECT)
+	if (!IsA(viewParse, Query))
+		elog(ERROR, "unexpected parse analysis result");
+	if (viewParse->utilityStmt != NULL &&
+		IsA(viewParse->utilityStmt, CreateTableAsStmt))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("views must not contain SELECT INTO")));
+	if (viewParse->commandType != CMD_SELECT ||
+		viewParse->utilityStmt != NULL)
 		elog(ERROR, "unexpected parse analysis result");
 
 	/*
@@ -449,10 +457,6 @@ DefineView(ViewStmt *stmt, const char *queryString)
 	 * DefineQueryRewrite(), but that function will complain about a bogus ON
 	 * SELECT rule, and we'd rather the message complain about a view.
 	 */
-	if (viewParse->intoClause != NULL)
-		ereport(ERROR,
-				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-				 errmsg("views must not contain SELECT INTO")));
 	if (viewParse->hasModifyingCTE)
 		ereport(ERROR,
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),