From fb34e94d214d6767910df47aa7c605c452d11c57 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Wed, 3 Oct 2012 19:47:11 -0400
Subject: [PATCH] Support CREATE SCHEMA IF NOT EXISTS.
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Per discussion, schema-element subcommands are not allowed together with
this option, since it's not very obvious what should happen to the element
objects.
FabrÃzio de Royes Mello
---
doc/src/sgml/ref/create_schema.sgml | 27 +++++++++++++++++++
src/backend/commands/extension.c | 1 +
src/backend/commands/schemacmds.c | 17 ++++++++++++
src/backend/nodes/copyfuncs.c | 1 +
src/backend/nodes/equalfuncs.c | 1 +
src/backend/parser/gram.y | 35 +++++++++++++++++++++++++
src/include/nodes/parsenodes.h | 1 +
src/test/regress/expected/namespace.out | 13 +++++++++
src/test/regress/sql/namespace.sql | 9 +++++++
9 files changed, 105 insertions(+)
diff --git a/doc/src/sgml/ref/create_schema.sgml b/doc/src/sgml/ref/create_schema.sgml
index 930d876814d..2602bb1d56f 100644
--- a/doc/src/sgml/ref/create_schema.sgml
+++ b/doc/src/sgml/ref/create_schema.sgml
@@ -23,6 +23,8 @@ PostgreSQL documentation
<synopsis>
CREATE SCHEMA <replaceable class="parameter">schema_name</replaceable> [ AUTHORIZATION <replaceable class="parameter">user_name</replaceable> ] [ <replaceable class="parameter">schema_element</replaceable> [ ... ] ]
CREATE SCHEMA AUTHORIZATION <replaceable class="parameter">user_name</replaceable> [ <replaceable class="parameter">schema_element</replaceable> [ ... ] ]
+CREATE SCHEMA IF NOT EXISTS <replaceable class="parameter">schema_name</replaceable> [ AUTHORIZATION <replaceable class="parameter">user_name</replaceable> ]
+CREATE SCHEMA IF NOT EXISTS AUTHORIZATION <replaceable class="parameter">user_name</replaceable>
</synopsis>
</refsynopsisdiv>
@@ -98,6 +100,17 @@ CREATE SCHEMA AUTHORIZATION <replaceable class="parameter">user_name</replaceabl
</para>
</listitem>
</varlistentry>
+
+ <varlistentry>
+ <term><literal>IF NOT EXISTS</literal></term>
+ <listitem>
+ <para>
+ Do nothing (except issuing a notice) if a schema with the same name
+ already exists. <replaceable class="parameter">schema_element</>
+ subcommands cannot be included when this option is used.
+ </para>
+ </listitem>
+ </varlistentry>
</variablelist>
</refsect1>
@@ -129,6 +142,15 @@ CREATE SCHEMA AUTHORIZATION joe;
</programlisting>
</para>
+ <para>
+ Create a schema named <literal>test</> that will be owned by user
+ <literal>joe</>, unless there already is a schema named <literal>test</>.
+ (It does not matter whether <literal>joe</> owns the pre-existing schema.)
+<programlisting>
+CREATE SCHEMA IF NOT EXISTS test AUTHORIZATION joe;
+</programlisting>
+ </para>
+
<para>
Create a schema and create a table and view within it:
<programlisting>
@@ -177,6 +199,11 @@ CREATE VIEW hollywood.winners AS
schema owner. This can happen only if the schema owner grants the
<literal>CREATE</> privilege on his schema to someone else.
</para>
+
+ <para>
+ The <literal>IF NOT EXISTS</literal> option is a
+ <productname>PostgreSQL</productname> extension.
+ </para>
</refsect1>
<refsect1>
diff --git a/src/backend/commands/extension.c b/src/backend/commands/extension.c
index 5712fe19c5c..5aa9bbb19c1 100644
--- a/src/backend/commands/extension.c
+++ b/src/backend/commands/extension.c
@@ -1376,6 +1376,7 @@ CreateExtension(CreateExtensionStmt *stmt)
csstmt->schemaname = schemaName;
csstmt->authid = NULL; /* will be created by current user */
csstmt->schemaElts = NIL;
+ csstmt->if_not_exists = false;
CreateSchemaCommand(csstmt, NULL);
/*
diff --git a/src/backend/commands/schemacmds.c b/src/backend/commands/schemacmds.c
index cd5ce06ca76..e69c86bbabf 100644
--- a/src/backend/commands/schemacmds.c
+++ b/src/backend/commands/schemacmds.c
@@ -83,6 +83,23 @@ CreateSchemaCommand(CreateSchemaStmt *stmt, const char *queryString)
errmsg("unacceptable schema name \"%s\"", schemaName),
errdetail("The prefix \"pg_\" is reserved for system schemas.")));
+ /*
+ * If if_not_exists was given and the schema already exists, bail out.
+ * (Note: we needn't check this when not if_not_exists, because
+ * NamespaceCreate will complain anyway.) We could do this before making
+ * the permissions checks, but since CREATE TABLE IF NOT EXISTS makes its
+ * creation-permission check first, we do likewise.
+ */
+ if (stmt->if_not_exists &&
+ SearchSysCacheExists1(NAMESPACENAME, PointerGetDatum(schemaName)))
+ {
+ ereport(NOTICE,
+ (errcode(ERRCODE_DUPLICATE_SCHEMA),
+ errmsg("schema \"%s\" already exists, skipping",
+ schemaName)));
+ return;
+ }
+
/*
* If the requested authorization is different from the current user,
* temporarily set the current user so that the object(s) will be created
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index 84ab16d61f1..9387ee90c9f 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -3613,6 +3613,7 @@ _copyCreateSchemaStmt(const CreateSchemaStmt *from)
COPY_STRING_FIELD(schemaname);
COPY_STRING_FIELD(authid);
COPY_NODE_FIELD(schemaElts);
+ COPY_SCALAR_FIELD(if_not_exists);
return newnode;
}
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index e537e43809c..226b99a1d27 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -1909,6 +1909,7 @@ _equalCreateSchemaStmt(const CreateSchemaStmt *a, const CreateSchemaStmt *b)
COMPARE_STRING_FIELD(schemaname);
COMPARE_STRING_FIELD(authid);
COMPARE_NODE_FIELD(schemaElts);
+ COMPARE_SCALAR_FIELD(if_not_exists);
return true;
}
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 62ff9178286..7feadeac169 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -1169,6 +1169,7 @@ CreateSchemaStmt:
n->schemaname = $5;
n->authid = $5;
n->schemaElts = $6;
+ n->if_not_exists = false;
$$ = (Node *)n;
}
| CREATE SCHEMA ColId OptSchemaEltList
@@ -1178,6 +1179,40 @@ CreateSchemaStmt:
n->schemaname = $3;
n->authid = NULL;
n->schemaElts = $4;
+ n->if_not_exists = false;
+ $$ = (Node *)n;
+ }
+ | CREATE SCHEMA IF_P NOT EXISTS OptSchemaName AUTHORIZATION RoleId OptSchemaEltList
+ {
+ CreateSchemaStmt *n = makeNode(CreateSchemaStmt);
+ /* One can omit the schema name or the authorization id. */
+ if ($6 != NULL)
+ n->schemaname = $6;
+ else
+ n->schemaname = $8;
+ n->authid = $8;
+ if ($9 != NIL)
+ ereport(ERROR,
+ (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+ errmsg("CREATE SCHEMA IF NOT EXISTS cannot include schema elements"),
+ parser_errposition(@9)));
+ n->schemaElts = $9;
+ n->if_not_exists = true;
+ $$ = (Node *)n;
+ }
+ | CREATE SCHEMA IF_P NOT EXISTS ColId OptSchemaEltList
+ {
+ CreateSchemaStmt *n = makeNode(CreateSchemaStmt);
+ /* ...but not both */
+ n->schemaname = $6;
+ n->authid = NULL;
+ if ($7 != NIL)
+ ereport(ERROR,
+ (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+ errmsg("CREATE SCHEMA IF NOT EXISTS cannot include schema elements"),
+ parser_errposition(@7)));
+ n->schemaElts = $7;
+ n->if_not_exists = true;
$$ = (Node *)n;
}
;
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index e10e3a1b345..09b15e7694c 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -1157,6 +1157,7 @@ typedef struct CreateSchemaStmt
char *schemaname; /* the name of the schema to create */
char *authid; /* the owner of the created schema */
List *schemaElts; /* schema components (list of parsenodes) */
+ bool if_not_exists; /* just do nothing if schema already exists? */
} CreateSchemaStmt;
typedef enum DropBehavior
diff --git a/src/test/regress/expected/namespace.out b/src/test/regress/expected/namespace.out
index 7c26da5636e..5fcd46daf42 100644
--- a/src/test/regress/expected/namespace.out
+++ b/src/test/regress/expected/namespace.out
@@ -36,6 +36,19 @@ SELECT * FROM test_schema_1.abc_view;
4 |
(3 rows)
+-- test IF NOT EXISTS cases
+CREATE SCHEMA test_schema_1; -- fail, already exists
+ERROR: schema "test_schema_1" already exists
+CREATE SCHEMA IF NOT EXISTS test_schema_1; -- ok with notice
+NOTICE: schema "test_schema_1" already exists, skipping
+CREATE SCHEMA IF NOT EXISTS test_schema_1 -- fail, disallowed
+ CREATE TABLE abc (
+ a serial,
+ b int UNIQUE
+ );
+ERROR: CREATE SCHEMA IF NOT EXISTS cannot include schema elements
+LINE 1: CREATE SCHEMA IF NOT EXISTS test_schema_1
+ ^
DROP SCHEMA test_schema_1 CASCADE;
NOTICE: drop cascades to 2 other objects
DETAIL: drop cascades to table test_schema_1.abc
diff --git a/src/test/regress/sql/namespace.sql b/src/test/regress/sql/namespace.sql
index 919f72ada2b..879b6c35b05 100644
--- a/src/test/regress/sql/namespace.sql
+++ b/src/test/regress/sql/namespace.sql
@@ -24,6 +24,15 @@ INSERT INTO test_schema_1.abc DEFAULT VALUES;
SELECT * FROM test_schema_1.abc;
SELECT * FROM test_schema_1.abc_view;
+-- test IF NOT EXISTS cases
+CREATE SCHEMA test_schema_1; -- fail, already exists
+CREATE SCHEMA IF NOT EXISTS test_schema_1; -- ok with notice
+CREATE SCHEMA IF NOT EXISTS test_schema_1 -- fail, disallowed
+ CREATE TABLE abc (
+ a serial,
+ b int UNIQUE
+ );
+
DROP SCHEMA test_schema_1 CASCADE;
-- verify that the objects were dropped
--
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