On Tue, Apr 1, 2014 at 2:46 PM, Robert Haas <[email protected]> wrote:
>
> >> Where this is a bit more interesting is in the case of sequences, where
> >> resetting the sequence to zero may cause further inserts into an
> >> existing table to fail.
> >
> > Yeah. Sequences do have contained data, which makes COR harder to
define
> > --- that's part of the reason why we have CINE not COR for tables, and
> > maybe we have to do the same for sequences. The point being exactly
> > that if you use CINE, you're implicitly accepting that you don't know
> > the ensuing state fully.
>
> Yeah. I think CINE is more sensible than COR for sequences, for
> precisely the reason that they do have contained data (even if it's
> basically only one value).
>
The attached patch contains CINE for sequences.
I just strip this code from the patch rejected before.
Regards,
--
Fabrízio de Royes Mello
Consultoria/Coaching PostgreSQL
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diff --git a/doc/src/sgml/ref/create_sequence.sgml b/doc/src/sgml/ref/create_sequence.sgml
index 70b9f3d..de85b18 100644
--- a/doc/src/sgml/ref/create_sequence.sgml
+++ b/doc/src/sgml/ref/create_sequence.sgml
@@ -21,7 +21,7 @@ PostgreSQL documentation
<refsynopsisdiv>
<synopsis>
-CREATE [ TEMPORARY | TEMP ] SEQUENCE <replaceable class="parameter">name</replaceable> [ INCREMENT [ BY ] <replaceable class="parameter">increment</replaceable> ]
+CREATE [ TEMPORARY | TEMP ] [ IF NOT EXISTS ] SEQUENCE <replaceable class="parameter">name</replaceable> [ INCREMENT [ BY ] <replaceable class="parameter">increment</replaceable> ]
[ MINVALUE <replaceable class="parameter">minvalue</replaceable> | NO MINVALUE ] [ MAXVALUE <replaceable class="parameter">maxvalue</replaceable> | NO MAXVALUE ]
[ START [ WITH ] <replaceable class="parameter">start</replaceable> ] [ CACHE <replaceable class="parameter">cache</replaceable> ] [ [ NO ] CYCLE ]
[ OWNED BY { <replaceable class="parameter">table_name</replaceable>.<replaceable class="parameter">column_name</replaceable> | NONE } ]
@@ -90,6 +90,16 @@ SELECT * FROM <replaceable>name</replaceable>;
</varlistentry>
<varlistentry>
+ <term><literal>IF NOT EXISTS</literal></term>
+ <listitem>
+ <para>
+ Do nothing (except issuing a notice) if a sequence with the same name
+ already exists.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
<term><replaceable class="parameter">name</replaceable></term>
<listitem>
<para>
diff --git a/src/backend/commands/sequence.c b/src/backend/commands/sequence.c
index ed696be..54be1b8 100644
--- a/src/backend/commands/sequence.c
+++ b/src/backend/commands/sequence.c
@@ -122,6 +122,17 @@ DefineSequence(CreateSeqStmt *seq)
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("unlogged sequences are not supported")));
+ /* Check for IF NOT EXISTS clause */
+ RangeVarGetAndCheckCreationNamespace(seq->sequence, NoLock, &seqoid);
+ if (seq->if_not_exists && OidIsValid(seqoid))
+ {
+ ereport(NOTICE,
+ (errcode(ERRCODE_DUPLICATE_TABLE),
+ errmsg("relation \"%s\" already exists, skipping",
+ seq->sequence->relname)));
+ return seqoid;
+ }
+
/* Check and set all option values */
init_params(seq->options, true, &new, &owned_by);
@@ -210,7 +221,7 @@ DefineSequence(CreateSeqStmt *seq)
stmt->options = NIL;
stmt->oncommit = ONCOMMIT_NOOP;
stmt->tablespacename = NULL;
- stmt->if_not_exists = false;
+ stmt->if_not_exists = seq->if_not_exists;
seqoid = DefineRelation(stmt, RELKIND_SEQUENCE, seq->ownerId);
Assert(seqoid != InvalidOid);
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index 98ad910..fecf4b7 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -3317,6 +3317,7 @@ _copyCreateSeqStmt(const CreateSeqStmt *from)
COPY_NODE_FIELD(sequence);
COPY_NODE_FIELD(options);
COPY_SCALAR_FIELD(ownerId);
+ COPY_SCALAR_FIELD(if_not_exists);
return newnode;
}
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index 9901d23..21663fb 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -1565,6 +1565,7 @@ _equalCreateSeqStmt(const CreateSeqStmt *a, const CreateSeqStmt *b)
COMPARE_NODE_FIELD(sequence);
COMPARE_NODE_FIELD(options);
COMPARE_SCALAR_FIELD(ownerId);
+ COMPARE_SCALAR_FIELD(if_not_exists);
return true;
}
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 7b9895d..27c24ea 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -3391,6 +3391,17 @@ CreateSeqStmt:
n->sequence = $4;
n->options = $5;
n->ownerId = InvalidOid;
+ n->if_not_exists = false;
+ $$ = (Node *)n;
+ }
+ | CREATE OptTemp SEQUENCE IF_P NOT EXISTS qualified_name OptSeqOptList
+ {
+ CreateSeqStmt *n = makeNode(CreateSeqStmt);
+ $7->relpersistence = $2;
+ n->sequence = $7;
+ n->options = $8;
+ n->ownerId = InvalidOid;
+ n->if_not_exists = true;
$$ = (Node *)n;
}
;
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 18d4991..3facff7 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -1941,6 +1941,7 @@ typedef struct CreateSeqStmt
RangeVar *sequence; /* the sequence to create */
List *options;
Oid ownerId; /* ID of owner, or InvalidOid for default */
+ bool if_not_exists; /* skip error if a Sequence already exists */
} CreateSeqStmt;
typedef struct AlterSeqStmt
diff --git a/src/test/regress/expected/sequence.out b/src/test/regress/expected/sequence.out
index 8fcb700..a27b5fd 100644
--- a/src/test/regress/expected/sequence.out
+++ b/src/test/regress/expected/sequence.out
@@ -91,6 +91,8 @@ SELECT nextval('serialTest2_f6_seq');
-- basic sequence operations using both text and oid references
CREATE SEQUENCE sequence_test;
+CREATE SEQUENCE IF NOT EXISTS sequence_test;
+NOTICE: relation "sequence_test" already exists, skipping
SELECT nextval('sequence_test'::text);
nextval
---------
diff --git a/src/test/regress/sql/sequence.sql b/src/test/regress/sql/sequence.sql
index be5e9a9..8d3b700 100644
--- a/src/test/regress/sql/sequence.sql
+++ b/src/test/regress/sql/sequence.sql
@@ -59,6 +59,7 @@ SELECT nextval('serialTest2_f6_seq');
-- basic sequence operations using both text and oid references
CREATE SEQUENCE sequence_test;
+CREATE SEQUENCE IF NOT EXISTS sequence_test;
SELECT nextval('sequence_test'::text);
SELECT nextval('sequence_test'::regclass);
--
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