On Tue, Dec 22, 2020 at 03:12:15PM +0530, Bharath Rupireddy wrote: > On Tue, Dec 22, 2020 at 2:07 PM Michael Paquier <mich...@paquier.xyz> wrote: >> Note: I'd like to think that we could choose a better name for >> CheckRelExistenceInCTAS(). > > I changed it to IsCTASRelCreationAllowed() and attached a v5 patch. > Please let me know if this is okay.
After thinking about that, using "CTAS" while other routines in the same area use "CreateTableAs" looks inconsistent to me. So I have come up with CreateTableAsRelExists() as name. As the same time, I have looked at the git history to note 9bd27b7 where we had better not give an empty output for non-text formats. So I'd like to think that it makes sense to use ExplainDummyGroup() if the relation exists with IF NOT EXISTS, keeping some consistency. What do you think? -- Michael
From ed6fb44e5433b86fbed454f1b52aaa8538a377ae Mon Sep 17 00:00:00 2001
From: Michael Paquier <mich...@paquier.xyz>
Date: Wed, 23 Dec 2020 21:28:07 +0900
Subject: [PATCH v6] Fail Fast In CTAS/CMV If Relation Already Exists
Currently, for CTAS or CREATE MATERIALIZED VIEW(CMV) without
IF-NOT-EXISTS clause, the existence of the relation (either
table or materialized view) gets checked during execution and an
error is thrown there. All the unnecessary rewrite and planning
for the SELECT part of the query have happened just to fail
later. However, if IF-NOT-EXISTS clause is present, then a notice
is issued and returned immediately without rewrite and planning
further. This seems somewhat inconsistent.
This patch propose to check the relation existence early in
ExecCreateTableAs() as well as in ExplainOneUtility() and
throw an error in case it exists already to avoid unnecessary
rewrite, planning and execution of the SELECT part.
---
src/include/commands/createas.h | 2 +
src/backend/commands/createas.c | 53 ++++++++++++++++-------
src/backend/commands/explain.c | 13 ++++++
src/test/regress/expected/matview.out | 38 ++++++++++++++++
src/test/regress/expected/select_into.out | 42 ++++++++++++++++++
src/test/regress/sql/matview.sql | 23 ++++++++++
src/test/regress/sql/select_into.sql | 21 +++++++++
7 files changed, 177 insertions(+), 15 deletions(-)
diff --git a/src/include/commands/createas.h b/src/include/commands/createas.h
index 7629230254..d8cfb62522 100644
--- a/src/include/commands/createas.h
+++ b/src/include/commands/createas.h
@@ -29,4 +29,6 @@ extern int GetIntoRelEFlags(IntoClause *intoClause);
extern DestReceiver *CreateIntoRelDestReceiver(IntoClause *intoClause);
+extern bool CreateTableAsRelExists(CreateTableAsStmt *ctas);
+
#endif /* CREATEAS_H */
diff --git a/src/backend/commands/createas.c b/src/backend/commands/createas.c
index 6bf6c5a310..01c94f1bce 100644
--- a/src/backend/commands/createas.c
+++ b/src/backend/commands/createas.c
@@ -239,21 +239,9 @@ ExecCreateTableAs(ParseState *pstate, CreateTableAsStmt *stmt,
PlannedStmt *plan;
QueryDesc *queryDesc;
- if (stmt->if_not_exists)
- {
- Oid nspid;
-
- nspid = RangeVarGetCreationNamespace(stmt->into->rel);
-
- if (get_relname_relid(stmt->into->rel->relname, nspid))
- {
- ereport(NOTICE,
- (errcode(ERRCODE_DUPLICATE_TABLE),
- errmsg("relation \"%s\" already exists, skipping",
- stmt->into->rel->relname)));
- return InvalidObjectAddress;
- }
- }
+ /* Check if the relation exists or not */
+ if (!CreateTableAsRelExists(stmt))
+ return InvalidObjectAddress;
/*
* Create the tuple receiver object and insert info it will need
@@ -400,6 +388,41 @@ GetIntoRelEFlags(IntoClause *intoClause)
return flags;
}
+/*
+ * CreateTableAsRelExists --- check existence of relation for CreateTableAsStmt
+ *
+ * Utility wrapper checking if the relation pending for creation in the
+ * CreateTableAsStmt query already exists or not. Returns true if the
+ * relation can be created.
+ */
+bool
+CreateTableAsRelExists(CreateTableAsStmt *ctas)
+{
+ Oid nspid;
+ IntoClause *into = ctas->into;
+
+ nspid = RangeVarGetCreationNamespace(into->rel);
+
+ if (get_relname_relid(into->rel->relname, nspid))
+ {
+ if (!ctas->if_not_exists)
+ ereport(ERROR,
+ (errcode(ERRCODE_DUPLICATE_TABLE),
+ errmsg("relation \"%s\" already exists",
+ into->rel->relname)));
+
+ /* The relation exists and IF NOT EXISTS has been specified */
+ ereport(NOTICE,
+ (errcode(ERRCODE_DUPLICATE_TABLE),
+ errmsg("relation \"%s\" already exists, skipping",
+ into->rel->relname)));
+ return false;
+ }
+
+ /* Relation does not exist, it can be created */
+ return true;
+}
+
/*
* CreateIntoRelDestReceiver -- create a suitable DestReceiver object
*
diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index 43f9b01e83..c2dd38f72b 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -435,6 +435,19 @@ 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);
+ return;
+ }
+
rewritten = QueryRewrite(castNode(Query, copyObject(ctas->query)));
Assert(list_length(rewritten) == 1);
ExplainOneQuery(linitial_node(Query, rewritten),
diff --git a/src/test/regress/expected/matview.out b/src/test/regress/expected/matview.out
index 2c0760404d..4b3a2e0cb7 100644
--- a/src/test/regress/expected/matview.out
+++ b/src/test/regress/expected/matview.out
@@ -630,3 +630,41 @@ drop cascades to materialized view matview_schema.mv_withdata2
drop cascades to materialized view matview_schema.mv_nodata1
drop cascades to materialized view matview_schema.mv_nodata2
DROP USER regress_matview_user;
+-- CREATE MATERIALIZED VIEW ... IF NOT EXISTS
+CREATE MATERIALIZED VIEW matview_ine_tab AS SELECT 1;
+CREATE MATERIALIZED VIEW matview_ine_tab AS SELECT 1 / 0; -- error
+ERROR: relation "matview_ine_tab" already exists
+CREATE MATERIALIZED VIEW IF NOT EXISTS matview_ine_tab AS
+ SELECT 1 / 0; -- ok
+NOTICE: relation "matview_ine_tab" already exists, skipping
+CREATE MATERIALIZED VIEW matview_ine_tab AS
+ SELECT 1 / 0 WITH NO DATA; -- error
+ERROR: relation "matview_ine_tab" already exists
+CREATE MATERIALIZED VIEW IF NOT EXISTS matview_ine_tab AS
+ SELECT 1 / 0 WITH NO DATA; -- ok
+NOTICE: relation "matview_ine_tab" already exists, skipping
+EXPLAIN (ANALYZE, COSTS OFF, SUMMARY OFF, TIMING OFF)
+ CREATE MATERIALIZED VIEW matview_ine_tab AS
+ SELECT 1 / 0; -- error
+ERROR: relation "matview_ine_tab" already exists
+EXPLAIN (ANALYZE, COSTS OFF, SUMMARY OFF, TIMING OFF)
+ CREATE MATERIALIZED VIEW IF NOT EXISTS matview_ine_tab AS
+ SELECT 1 / 0; -- ok
+NOTICE: relation "matview_ine_tab" already exists, skipping
+ QUERY PLAN
+------------
+(0 rows)
+
+EXPLAIN (ANALYZE, COSTS OFF, SUMMARY OFF, TIMING OFF)
+ CREATE MATERIALIZED VIEW matview_ine_tab AS
+ SELECT 1 / 0 WITH NO DATA; -- error
+ERROR: relation "matview_ine_tab" already exists
+EXPLAIN (ANALYZE, COSTS OFF, SUMMARY OFF, TIMING OFF)
+ CREATE MATERIALIZED VIEW IF NOT EXISTS matview_ine_tab AS
+ SELECT 1 / 0 WITH NO DATA; -- ok
+NOTICE: relation "matview_ine_tab" already exists, skipping
+ QUERY PLAN
+------------
+(0 rows)
+
+DROP MATERIALIZED VIEW matview_ine_tab;
diff --git a/src/test/regress/expected/select_into.out b/src/test/regress/expected/select_into.out
index bf5c6bea04..43b8209d22 100644
--- a/src/test/regress/expected/select_into.out
+++ b/src/test/regress/expected/select_into.out
@@ -178,3 +178,45 @@ INSERT INTO b SELECT 1 INTO f;
ERROR: SELECT ... INTO is not allowed here
LINE 1: INSERT INTO b SELECT 1 INTO f;
^
+-- Test CREATE TABLE AS ... IF NOT EXISTS
+CREATE TABLE ctas_ine_tbl AS SELECT 1;
+CREATE TABLE ctas_ine_tbl AS SELECT 1 / 0; -- error
+ERROR: relation "ctas_ine_tbl" already exists
+CREATE TABLE IF NOT EXISTS ctas_ine_tbl AS SELECT 1 / 0; -- ok
+NOTICE: relation "ctas_ine_tbl" already exists, skipping
+CREATE TABLE ctas_ine_tbl AS SELECT 1 / 0 WITH NO DATA; -- error
+ERROR: relation "ctas_ine_tbl" already exists
+CREATE TABLE IF NOT EXISTS ctas_ine_tbl AS SELECT 1 / 0 WITH NO DATA; -- ok
+NOTICE: relation "ctas_ine_tbl" already exists, skipping
+EXPLAIN (ANALYZE, COSTS OFF, SUMMARY OFF, TIMING OFF)
+ CREATE TABLE ctas_ine_tbl AS SELECT 1 / 0; -- error
+ERROR: relation "ctas_ine_tbl" already exists
+EXPLAIN (ANALYZE, COSTS OFF, SUMMARY OFF, TIMING OFF)
+ CREATE TABLE IF NOT EXISTS ctas_ine_tbl AS SELECT 1 / 0; -- ok
+NOTICE: relation "ctas_ine_tbl" already exists, skipping
+ QUERY PLAN
+------------
+(0 rows)
+
+EXPLAIN (ANALYZE, COSTS OFF, SUMMARY OFF, TIMING OFF)
+ CREATE TABLE ctas_ine_tbl AS SELECT 1 / 0 WITH NO DATA; -- error
+ERROR: relation "ctas_ine_tbl" already exists
+EXPLAIN (ANALYZE, COSTS OFF, SUMMARY OFF, TIMING OFF)
+ CREATE TABLE IF NOT EXISTS ctas_ine_tbl AS SELECT 1 / 0 WITH NO DATA; -- ok
+NOTICE: relation "ctas_ine_tbl" already exists, skipping
+ QUERY PLAN
+------------
+(0 rows)
+
+PREPARE ctas_ine_query AS SELECT 1 / 0;
+EXPLAIN (ANALYZE, COSTS OFF, SUMMARY OFF, TIMING OFF)
+ CREATE TABLE ctas_ine_tbl AS EXECUTE ctas_ine_query; -- error
+ERROR: relation "ctas_ine_tbl" already exists
+EXPLAIN (ANALYZE, COSTS OFF, SUMMARY OFF, TIMING OFF)
+ CREATE TABLE IF NOT EXISTS ctas_ine_tbl AS EXECUTE ctas_ine_query; -- ok
+NOTICE: relation "ctas_ine_tbl" already exists, skipping
+ QUERY PLAN
+------------
+(0 rows)
+
+DROP TABLE ctas_ine_tbl;
diff --git a/src/test/regress/sql/matview.sql b/src/test/regress/sql/matview.sql
index 70c4954d89..4a4bd0d6b6 100644
--- a/src/test/regress/sql/matview.sql
+++ b/src/test/regress/sql/matview.sql
@@ -264,3 +264,26 @@ ALTER DEFAULT PRIVILEGES FOR ROLE regress_matview_user
DROP SCHEMA matview_schema CASCADE;
DROP USER regress_matview_user;
+
+-- CREATE MATERIALIZED VIEW ... IF NOT EXISTS
+CREATE MATERIALIZED VIEW matview_ine_tab AS SELECT 1;
+CREATE MATERIALIZED VIEW matview_ine_tab AS SELECT 1 / 0; -- error
+CREATE MATERIALIZED VIEW IF NOT EXISTS matview_ine_tab AS
+ SELECT 1 / 0; -- ok
+CREATE MATERIALIZED VIEW matview_ine_tab AS
+ SELECT 1 / 0 WITH NO DATA; -- error
+CREATE MATERIALIZED VIEW IF NOT EXISTS matview_ine_tab AS
+ SELECT 1 / 0 WITH NO DATA; -- ok
+EXPLAIN (ANALYZE, COSTS OFF, SUMMARY OFF, TIMING OFF)
+ CREATE MATERIALIZED VIEW matview_ine_tab AS
+ SELECT 1 / 0; -- error
+EXPLAIN (ANALYZE, COSTS OFF, SUMMARY OFF, TIMING OFF)
+ CREATE MATERIALIZED VIEW IF NOT EXISTS matview_ine_tab AS
+ SELECT 1 / 0; -- ok
+EXPLAIN (ANALYZE, COSTS OFF, SUMMARY OFF, TIMING OFF)
+ CREATE MATERIALIZED VIEW matview_ine_tab AS
+ SELECT 1 / 0 WITH NO DATA; -- error
+EXPLAIN (ANALYZE, COSTS OFF, SUMMARY OFF, TIMING OFF)
+ CREATE MATERIALIZED VIEW IF NOT EXISTS matview_ine_tab AS
+ SELECT 1 / 0 WITH NO DATA; -- ok
+DROP MATERIALIZED VIEW matview_ine_tab;
diff --git a/src/test/regress/sql/select_into.sql b/src/test/regress/sql/select_into.sql
index 6c170ef968..7e903c339a 100644
--- a/src/test/regress/sql/select_into.sql
+++ b/src/test/regress/sql/select_into.sql
@@ -115,3 +115,24 @@ COPY (SELECT 1 INTO frak UNION SELECT 2) TO 'blob';
SELECT * FROM (SELECT 1 INTO f) bar;
CREATE VIEW foo AS SELECT 1 INTO b;
INSERT INTO b SELECT 1 INTO f;
+
+-- Test CREATE TABLE AS ... IF NOT EXISTS
+CREATE TABLE ctas_ine_tbl AS SELECT 1;
+CREATE TABLE ctas_ine_tbl AS SELECT 1 / 0; -- error
+CREATE TABLE IF NOT EXISTS ctas_ine_tbl AS SELECT 1 / 0; -- ok
+CREATE TABLE ctas_ine_tbl AS SELECT 1 / 0 WITH NO DATA; -- error
+CREATE TABLE IF NOT EXISTS ctas_ine_tbl AS SELECT 1 / 0 WITH NO DATA; -- ok
+EXPLAIN (ANALYZE, COSTS OFF, SUMMARY OFF, TIMING OFF)
+ CREATE TABLE ctas_ine_tbl AS SELECT 1 / 0; -- error
+EXPLAIN (ANALYZE, COSTS OFF, SUMMARY OFF, TIMING OFF)
+ CREATE TABLE IF NOT EXISTS ctas_ine_tbl AS SELECT 1 / 0; -- ok
+EXPLAIN (ANALYZE, COSTS OFF, SUMMARY OFF, TIMING OFF)
+ CREATE TABLE ctas_ine_tbl AS SELECT 1 / 0 WITH NO DATA; -- error
+EXPLAIN (ANALYZE, COSTS OFF, SUMMARY OFF, TIMING OFF)
+ CREATE TABLE IF NOT EXISTS ctas_ine_tbl AS SELECT 1 / 0 WITH NO DATA; -- ok
+PREPARE ctas_ine_query AS SELECT 1 / 0;
+EXPLAIN (ANALYZE, COSTS OFF, SUMMARY OFF, TIMING OFF)
+ CREATE TABLE ctas_ine_tbl AS EXECUTE ctas_ine_query; -- error
+EXPLAIN (ANALYZE, COSTS OFF, SUMMARY OFF, TIMING OFF)
+ CREATE TABLE IF NOT EXISTS ctas_ine_tbl AS EXECUTE ctas_ine_query; -- ok
+DROP TABLE ctas_ine_tbl;
--
2.29.2
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