From e665769e6d1e84b6650f53ed297058fc11152f7f Mon Sep 17 00:00:00 2001 From: Michael Paquier Date: Wed, 30 Dec 2020 21:23:24 +0900 Subject: Sanitize IF NOT EXISTS in EXPLAIN for CTAS and matviews IF NOT EXISTS was ignored when specified in an EXPLAIN query for CREATE MATERIALIZED VIEW or CREATE TABLE AS. Hence, if this clause was specified, the caller would get a failure if the relation already exists instead of a success with a NOTICE message. This commit makes the behavior of IF NOT EXISTS in EXPLAIN consistent with the non-EXPLAIN'd DDL queries, preventing a failure with IF NOT EXISTS if the relation to-be-created already exists. The skip is done before the SELECT query used for the relation is planned or executed, and a "dummy" plan is generated instead depending on the format used by EXPLAIN. Author: Bharath Rupireddy Reviewed-by: Zhijie Hou, Michael Paquier Discussion: https://postgr.es/m/CALj2ACVa3oJ9O_wcGd+FtHWZds04dEKcakxphGz5POVgD4wC7Q@mail.gmail.com --- src/backend/commands/explain.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) (limited to 'src/backend/commands/explain.c') diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c index 43f9b01e833..d797b5f53e0 100644 --- a/src/backend/commands/explain.c +++ b/src/backend/commands/explain.c @@ -435,6 +435,22 @@ ExplainOneUtility(Node *utilityStmt, IntoClause *into, ExplainState *es, CreateTableAsStmt *ctas = (CreateTableAsStmt *) utilityStmt; List *rewritten; + /* + * Check if the relation exists or not. This is done at this stage to + * avoid query planning or execution. + */ + if (CreateTableAsRelExists(ctas)) + { + if (ctas->objtype == OBJECT_TABLE) + ExplainDummyGroup("CREATE TABLE AS", NULL, es); + else if (ctas->objtype == OBJECT_MATVIEW) + ExplainDummyGroup("CREATE MATERIALIZED VIEW", NULL, es); + else + elog(ERROR, "unexpected object type: %d", + (int) ctas->objtype); + return; + } + rewritten = QueryRewrite(castNode(Query, copyObject(ctas->query))); Assert(list_length(rewritten) == 1); ExplainOneQuery(linitial_node(Query, rewritten), -- cgit v1.2.3