添加create if not exists语法

doc/src/sgml/ref/create_sequence.sgmlin

@@ -16,7 +16,7 @@
 
  <refsynopsisdiv>
 <synopsis>
-CREATE [ LARGE ] SEQUENCE <replaceable class="parameter">name</replaceable> [ INCREMENT [ BY ] <replaceable class="parameter">increment</replaceable> ]
+CREATE [ LARGE ] SEQUENCE [ IF NOT EXISTS ] <replaceable class="parameter">name</replaceable> [ INCREMENT [ BY ] <replaceable class="parameter">increment</replaceable> ]
     [ MINVALUE <replaceable class="parameter">minvalue</replaceable> | NO MINVALUE | NOMINVALUE] [ MAXVALUE <replaceable class="parameter">maxvalue</replaceable> | NO MAXVALUE | NOMAXVALUE]
     [ START [ WITH ] <replaceable class="parameter">start</replaceable> ] [ CACHE <replaceable class="parameter">cache</replaceable> ] [ [ NO ] CYCLE | NOCYCLE]
     [ OWNED BY { <replaceable class="parameter">table_name</replaceable>.<replaceable class="parameter">column_name</replaceable> | NONE } ];

src/common/backend/nodes/copyfuncs.cpp

@@ -5901,6 +5901,7 @@ static CreateSeqStmt* _copyCreateSeqStmt(const CreateSeqStmt* from)
     COPY_SCALAR_FIELD(uuid);
     COPY_SCALAR_FIELD(canCreateTempSeq);
     COPY_SCALAR_FIELD(is_large);
+    COPY_SCALAR_FIELD(missing_ok);
 
     return newnode;
 }

src/common/backend/nodes/equalfuncs.cpp

@@ -1893,6 +1893,7 @@ static bool _equalCreateSeqStmt(const CreateSeqStmt* a, const CreateSeqStmt* b)
     COMPARE_SCALAR_FIELD(uuid);
     COMPARE_SCALAR_FIELD(canCreateTempSeq);
     COMPARE_SCALAR_FIELD(is_large);
+    COMPARE_SCALAR_FIELD(missing_ok);
 
     return true;
 }

src/common/backend/parser/gram.y

@@ -9861,6 +9861,34 @@ CreateSeqStmt:
 
 					n->sequence = $5;
 					n->options = $6;
+					n->missing_ok = false;
+					n->ownerId = InvalidOid;
+/* PGXC_BEGIN */
+					n->is_serial = false;
+/* PGXC_END */
+					n->uuid = 0;
+					n->canCreateTempSeq = false;
+					$$ = (Node *)n;
+				}
+			| CREATE OptTemp opt_large_seq SEQUENCE IF_P NOT EXISTS qualified_name OptSeqOptList
+				{
+					CreateSeqStmt *n = makeNode(CreateSeqStmt);
+					$8->relpersistence = $2;
+					n->is_large = $3;
+#ifdef ENABLE_MULTIPLE_NODES
+					if (n->is_large) {
+        				const char* message = "large sequence is not supported.";
+    					InsertErrorMessage(message, u_sess->plsql_cxt.plpgsql_yylloc);
+						ereport(ERROR,
+							(errmodule(MOD_PARSER),
+								errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+								errmsg("large sequence is not supported.")));
+					}
+#endif
+
+					n->sequence = $8;
+					n->options = $9;
+					n->missing_ok = true;
 					n->ownerId = InvalidOid;
 /* PGXC_BEGIN */
 					n->is_serial = false;

src/gausskernel/optimizer/commands/sequence/sequence.cpp

@@ -821,6 +821,18 @@ static ObjectAddress DefineSequence(CreateSeqStmt* seq)
     bool isUseLocalSeq = false;
     Oid namespaceOid = InvalidOid;
     ObjectAddress address;
+    Oid existing_relid = InvalidOid;
+    Oid namespaceId = InvalidOid;
+    char rel_kind = large ? RELKIND_LARGE_SEQUENCE : RELKIND_SEQUENCE;
+
+    if (seq->missing_ok) {
+        namespaceId = RangeVarGetAndCheckCreationNamespace(seq->sequence, NoLock, &existing_relid, rel_kind);
+        if (existing_relid != InvalidOid) {
+            char* namespace_of_existing_rel = get_namespace_name(namespaceId);
+            ereport(NOTICE, (errmodule(MOD_COMMAND), errmsg("relation \"%s\" already exists in schema \"%s\", skipping", seq->sequence->relname, namespace_of_existing_rel)));
+            return InvalidObjectAddress;
+        }
+    }
 
 #ifdef PGXC /* PGXC_COORD */
     GTM_Sequence start_value = 1;
@@ -996,7 +1008,6 @@ static ObjectAddress DefineSequence(CreateSeqStmt* seq)
     stmt->tablespacename = NULL;
     stmt->if_not_exists = false;
     stmt->charset = PG_INVALID_ENCODING;
-    char rel_kind = large ? RELKIND_LARGE_SEQUENCE : RELKIND_SEQUENCE;
     address = DefineRelation(stmt, rel_kind, seq->ownerId, NULL);
     seqoid = address.objectId;
     Assert(seqoid != InvalidOid);

src/include/nodes/parsenodes.h

@@ -1131,6 +1131,7 @@ typedef struct CreateSeqStmt {
     int64 uuid;            /* UUID of the sequence, mark unique sequence globally */
     bool canCreateTempSeq; /* create sequence when "create table (like )" */
     bool is_large;
+    bool missing_ok; /* skip error if a Sequence is exists */
 } CreateSeqStmt;
 
 typedef struct AlterSeqStmt {

src/test/regress/expected/test_create_sequence_if_not_exists.out

@@ -0,0 +1,14 @@
+create schema create_sequence_if_not_exists;
+set current_schema = create_sequence_if_not_exists;
+create sequence seq start with 1;
+create sequence seq start with 1;
+ERROR:  relation "seq" already exists in schema "create_sequence_if_not_exists"
+DETAIL:  creating new table with existing name in the same schema
+create sequence if not exists seq start with 1;
+NOTICE:  relation "seq" already exists in schema "create_sequence_if_not_exists", skipping
+drop sequence seq;
+create sequence if not exists seq start with 1;
+create sequence if not exists seq start with 2;
+NOTICE:  relation "seq" already exists in schema "create_sequence_if_not_exists", skipping
+drop sequence seq;
+drop schema create_sequence_if_not_exists;

src/test/regress/parallel_schedule0

@@ -639,7 +639,7 @@ test: copy_new_gram copy_gbk_test copy_gb18030_test
 # Another group of parallel tests
 # ----------
 test: create_function_3 vacuum
-test: drop_if_exists drop_database test_if_not_exists test_create_index_if_not_exists
+test: drop_if_exists drop_database test_if_not_exists test_create_index_if_not_exists test_create_sequence_if_not_exists
 #test: constraints
 
 #test: errors subplan_base

src/test/regress/parallel_schedule0A

@@ -436,7 +436,7 @@ test: stable_function_shippable
 # Another group of parallel tests
 # ----------
 test: create_function_3 vacuum
-test: drop_if_exists drop_database test_if_not_exists test_create_index_if_not_exists
+test: drop_if_exists drop_database test_if_not_exists test_create_index_if_not_exists test_create_sequence_if_not_exists
 #test: constraints
 
 #test: errors subplan_base

src/test/regress/sql/test_create_sequence_if_not_exists.sql

@@ -0,0 +1,12 @@
+create schema create_sequence_if_not_exists;
+set current_schema = create_sequence_if_not_exists;
+
+create sequence seq start with 1;
+create sequence seq start with 1;
+
+create sequence if not exists seq start with 1;
+drop sequence seq;
+create sequence if not exists seq start with 1;
+create sequence if not exists seq start with 2;
+drop sequence seq;
+drop schema create_sequence_if_not_exists;