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

diff --git a/src/backend/commands/createas.c b/src/backend/commands/createas.c
index 6bf6c5a3106ff01cc2327f80dabffc5ee6bb6a80..009896bcee78c10edc7b824af163d33505e5b88a 100644 (file)
--- 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 this
+ * CreateTableAsStmt query already exists or not.  Returns true if the
+ * relation exists, otherwise false.
+ */
+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 true;
+   }
+
+   /* Relation does not exist, it can be created */
+   return false;
+}
+
 /*
  * CreateIntoRelDestReceiver -- create a suitable DestReceiver object
  *

diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index 43f9b01e833b1042723d308836423d53f915da3b..d797b5f53e039d8f2596a1367a2406f37cb329be 100644 (file)
--- 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),

diff --git a/src/include/commands/createas.h b/src/include/commands/createas.h
index 7629230254248feec36e3bdeb2425fdddd4fa607..d8cfb625228fcc368f0719cf67e9e159feceb92b 100644 (file)
--- 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/test/regress/expected/matview.out b/src/test/regress/expected/matview.out
index 2c0760404d3bbfd3cd405ea7de24c69eb873ac1e..4b3a2e0cb730637fe767b2730e60052cbba7201b 100644 (file)
--- 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 bf5c6bea045ee1eeadc04b604641eea59ab2496f..43b8209d229545de5b7729807c14816f13ef3d9d 100644 (file)
--- 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 70c4954d89a300dcd814c95d810b59dd3194715d..4a4bd0d6b6199c94c361403cf4fadd32194a67f9 100644 (file)
--- 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 6c170ef9688a1dfa3470fa17abe8d5ba22c41826..7e903c339a809328ced21cebc2e2e49007a59a6d 100644 (file)
--- 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;