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Make UtilityContainsQuery recurse until it finds a non-utility Query.

author Tom Lane <tgl@sss.pgh.pa.us>

2012年6月28日 03:18:30 +0000 (23:18 -0400)

committer Tom Lane <tgl@sss.pgh.pa.us>

2012年6月28日 03:18:30 +0000 (23:18 -0400)

The callers of UtilityContainsQuery want it to return a non-utility Query
if it returns anything at all. However, since we made CREATE TABLE
AS/SELECT INTO into a utility command instead of a variant of SELECT,
a command like "EXPLAIN SELECT INTO" results in two nested utility
statements. So what we need UtilityContainsQuery to do is drill down
to the bottom non-utility Query.

I had thought of this possibility in setrefs.c, and fixed it there by
looping around the UtilityContainsQuery call; but overlooked that the call
sites in plancache.c have a similar issue. In those cases it's
notationally inconvenient to provide an external loop, so let's redefine
UtilityContainsQuery as recursing down to a non-utility Query instead.

Noted by Rushabh Lathia. This is a somewhat cleaned-up version of his
proposed patch.

src/backend/optimizer/plan/setrefs.c patch | blob | blame | history

src/backend/tcop/utility.c patch | blob | blame | history

diff --git a/src/backend/optimizer/plan/setrefs.c b/src/backend/optimizer/plan/setrefs.c

index f375b5f76d4ded16f5045587d86f80cedeef82b3..ccd69fc3660652a1771c6394b14bd70b33441822 100644 (file)

--- a/src/backend/optimizer/plan/setrefs.c

+++ b/src/backend/optimizer/plan/setrefs.c

@@ -1937,7 +1937,7 @@ extract_query_dependencies_walker(Node *node, PlannerInfo *context)

Query *query = (Query *) node;

ListCell *lc;

- while (query->commandType == CMD_UTILITY)

+ if (query->commandType == CMD_UTILITY)

{

/*

* Ignore utility statements, except those (such as EXPLAIN) that

diff --git a/src/backend/tcop/utility.c b/src/backend/tcop/utility.c

index 8b73858300ee157c09f02f87a55a195f81a93913..33b292e6b7a9c1e47fb34de126cbc34dc5246693 100644 (file)

--- a/src/backend/tcop/utility.c

+++ b/src/backend/tcop/utility.c

@@ -1351,25 +1351,39 @@ QueryReturnsTuples(Query *parsetree)

* UtilityContainsQuery

* Return the contained Query, or NULL if there is none

*

- * Certain utility statements, such as EXPLAIN, contain a Query.

+ * Certain utility statements, such as EXPLAIN, contain a plannable Query.

* This function encapsulates knowledge of exactly which ones do.

* We assume it is invoked only on already-parse-analyzed statements

* (else the contained parsetree isn't a Query yet).

+ *

+ * In some cases (currently, only EXPLAIN of CREATE TABLE AS/SELECT INTO),

+ * potentially Query-containing utility statements can be nested. This

+ * function will drill down to a non-utility Query, or return NULL if none.

*/

Query *

UtilityContainsQuery(Node *parsetree)

{

+ Query *qry;

+

switch (nodeTag(parsetree))

{

case T_ExplainStmt:

- Assert(IsA(((ExplainStmt *) parsetree)->query, Query));

- return (Query *) ((ExplainStmt *) parsetree)->query;

+ qry = (Query *) ((ExplainStmt *) parsetree)->query;

+ Assert(IsA(qry, Query));

+ if (qry->commandType == CMD_UTILITY)

+ return UtilityContainsQuery(qry->utilityStmt);

+ return qry;

case T_CreateTableAsStmt:

/* might or might not contain a Query ... */

- if (IsA(((CreateTableAsStmt *) parsetree)->query, Query))

- return (Query *) ((CreateTableAsStmt *) parsetree)->query;

- Assert(IsA(((CreateTableAsStmt *) parsetree)->query, ExecuteStmt));

+ qry = (Query *) ((CreateTableAsStmt *) parsetree)->query;

+ if (IsA(qry, Query))

+ {

+ /* Recursion currently can't be necessary here */

+ Assert(qry->commandType != CMD_UTILITY);

+ return qry;

+ }

+ Assert(IsA(qry, ExecuteStmt));

return NULL;

default:

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