change create sentence in nGQL (#906)

docs-2.0/20.appendix/0.FAQ.md

@@ -143,8 +143,8 @@ See [show-stats](../3.ngql-guide/7.general-query-statements/6.show/14.show-stats
 1. Create and rebuild the index.
 
    ```ngql
-   > CREATE TAG INDEX i_player ON player();
-   > REBUILD TAG INDEX i_player;
+   > CREATE TAG INDEX IF NOT EXISTS i_player ON player();
+   > REBUILD TAG INDEX IF NOT EXISTS i_player;
    ```
 
 2. Use `LOOKUP` or `MATCH`. For example:
@@ -179,7 +179,7 @@ The graphd process requires `start vids` to begin a graph traversal. The `start
 It can also be found from a property index. For example:
 
 ```ngql
-# CREATE TAG INDEX i_player ON player(name(20));
+# CREATE TAG INDEX IF NOT EXISTS i_player ON player(name(20));
 # REBUILD TAG INDEX i_player;
 
 > LOOKUP ON player WHERE player.name == "abc" | ... YIELD ...

docs-2.0/20.appendix/identifier-case-sensitivity.md

@@ -5,7 +5,7 @@
 The following statements would not work because they refer to two different spaces, i.e. `my_space` and `MY_SPACE`:
 
 ```ngql
-nebula> CREATE SPACE my_space;
+nebula> CREATE SPACE IF NOT EXISTS my_space;
 nebula> use MY_SPACE;
 [ERROR (-8)]: SpaceNotFound:
 # my_space and MY_SPACE are two different spaces

docs-2.0/3.ngql-guide/1.nGQL-overview/1.overview.md

@@ -56,7 +56,7 @@ CREATE {TAG | EDGE} {<tag_name> | <edge_type>}(<property_name> <data_type>
 Example statement:
 
 ```ngql
-nebula> CREATE TAG player(name string, age int);
+nebula> CREATE TAG IF NOT EXISTS player(name string, age int);
 ```
 
 ## About openCypher compatibility

docs-2.0/3.ngql-guide/1.nGQL-overview/identifier-case-sensitivity.md

@@ -5,7 +5,7 @@
 The following statements will not work because they refer to two different spaces, i.e. `my_space` and `MY_SPACE`.
 
 ```ngql
-nebula> CREATE SPACE my_space (vid_type=FIXED_STRING(30));
+nebula> CREATE SPACE IF NOT EXISTS my_space (vid_type=FIXED_STRING(30));
 nebula> use MY_SPACE;
 [ERROR (-8)]: SpaceNotFound:
 ```

docs-2.0/3.ngql-guide/10.tag-statements/1.create-tag.md

@@ -43,16 +43,16 @@ CREATE TAG [IF NOT EXISTS] <tag_name>
 ### Examples
 
 ```ngql
-nebula> CREATE TAG player(name string, age int);
+nebula> CREATE TAG IF NOT EXISTS player(name string, age int);
 
 # The following example creates a tag with no properties.
-nebula> CREATE TAG no_property(); 
+nebula> CREATE TAG IF NOT EXISTS no_property(); 
 
 # The following example creates a tag with a default value.
-nebula> CREATE TAG player_with_default(name string, age int DEFAULT 20);
+nebula> CREATE TAG IF NOT EXISTS player_with_default(name string, age int DEFAULT 20);
 
 # In the following example, the TTL of the create_time field is set to be 100 seconds.
-nebula> CREATE TAG woman(name string, age int, \
+nebula> CREATE TAG IF NOT EXISTS woman(name string, age int, \
         married bool, salary double, create_time timestamp) \
         TTL_DURATION = 100, TTL_COL = "create_time";
 ```

docs-2.0/3.ngql-guide/10.tag-statements/2.drop-tag.md

@@ -29,7 +29,7 @@ DROP TAG [IF EXISTS] <tag_name>;
 ## Example
 
 ```ngql
-nebula> CREATE TAG test(p1 string, p2 int);
+nebula> CREATE TAG IF NOT EXISTS test(p1 string, p2 int);
 nebula> DROP TAG test;
 ```
 

docs-2.0/3.ngql-guide/10.tag-statements/3.alter-tag.md

@@ -32,7 +32,7 @@ ttl_definition:
 ## Examples
 
 ```ngql
-nebula> CREATE TAG t1 (p1 string, p2 int);
+nebula> CREATE TAG IF NOT EXISTS t1 (p1 string, p2 int);
 nebula> ALTER TAG t1 ADD (p3 int, p4 string);
 nebula> ALTER TAG t1 TTL_DURATION = 2, TTL_COL = "p2";
 nebula> ALTER TAG t1 COMMENT = 'test1';

docs-2.0/3.ngql-guide/10.tag-statements/6.delete-tag.md

@@ -25,8 +25,8 @@ DELETE TAG <tag_name_list> FROM <VID>;
 ## Example
 
 ```ngql
-nebula> CREATE TAG test1(p1 string, p2 int);
-nebula> CREATE TAG test2(p3 string, p4 int);
+nebula> CREATE TAG IF NOT EXISTS test1(p1 string, p2 int);
+nebula> CREATE TAG IF NOT EXISTS test2(p3 string, p4 int);
 nebula> INSERT VERTEX test1(p1, p2),test2(p3, p4) VALUES "test":("123", 1, "456", 2);
 nebula> FETCH PROP ON * "test";
 +------------------------------------------------------------+

docs-2.0/3.ngql-guide/10.tag-statements/improve-query-by-tag-index.md

@@ -14,8 +14,8 @@ For example, in the `basketballplayer` data set, some basketball players are als
 
 ```ngql
 //This example creates the shareholder tag and index.
-nebula> CREATE TAG shareholder();
-nebula> CREATE TAG INDEX shareholder_tag on shareholder();
+nebula> CREATE TAG IF NOT EXISTS shareholder();
+nebula> CREATE TAG INDEX IF NOT EXISTS shareholder_tag on shareholder();
 
 //This example adds a tag on the vertex.
 nebula> INSERT VERTEX shareholder() VALUES "player100":();

docs-2.0/3.ngql-guide/11.edge-type-statements/1.create-edge.md

@@ -43,16 +43,16 @@ CREATE EDGE [IF NOT EXISTS] <edge_type_name>
 ### Examples
 
 ```ngql
-nebula> CREATE EDGE follow(degree int);
+nebula> CREATE EDGE IF NOT EXISTS follow(degree int);
 
 # The following example creates an edge type with no properties.
-nebula> CREATE EDGE no_property();
+nebula> CREATE EDGE IF NOT EXISTS no_property();
 
 # The following example creates an edge type with a default value.
-nebula> CREATE EDGE follow_with_default(degree int DEFAULT 20);
+nebula> CREATE EDGE IF NOT EXISTS follow_with_default(degree int DEFAULT 20);
 
 # In the following example, the TTL of the p2 field is set to be 100 seconds.
-nebula> CREATE EDGE e1(p1 string, p2 int, p3 timestamp) \
+nebula> CREATE EDGE IF NOT EXISTS e1(p1 string, p2 int, p3 timestamp) \
         TTL_DURATION = 100, TTL_COL = "p2";
 ```
 

docs-2.0/3.ngql-guide/11.edge-type-statements/2.drop-edge.md

@@ -27,6 +27,6 @@ DROP EDGE [IF EXISTS] <edge_type_name>
 ## Example
 
 ```ngql
-nebula> CREATE EDGE e1(p1 string, p2 int);
+nebula> CREATE EDGE IF NOT EXISTS e1(p1 string, p2 int);
 nebula> DROP EDGE e1;
 ```

docs-2.0/3.ngql-guide/11.edge-type-statements/3.alter-edge.md

@@ -32,7 +32,7 @@ ttl_definition:
 ## Example
 
 ```ngql
-nebula> CREATE EDGE e1(p1 string, p2 int);
+nebula> CREATE EDGE IF NOT EXISTS e1(p1 string, p2 int);
 nebula> ALTER EDGE e1 ADD (p3 int, p4 string);
 nebula> ALTER EDGE e1 TTL_DURATION = 2, TTL_COL = "p2";
 nebula> ALTER EDGE e1 COMMENT = 'edge1';

docs-2.0/3.ngql-guide/12.vertex-statements/1.insert-vertex.md

@@ -48,12 +48,12 @@ Examples are as follows.
 
 ```ngql
 # The following examples create tag t1 with no property and inserts vertex "10" with no property.
-nebula> CREATE TAG t1();                   
+nebula> CREATE TAG IF NOT EXISTS t1();                   
 nebula> INSERT VERTEX t1() VALUE "10":(); 
 ```
 
 ```ngql
-nebula> CREATE TAG t2 (name string, age int);                
+nebula> CREATE TAG IF NOT EXISTS t2 (name string, age int);                
 nebula> INSERT VERTEX t2 (name, age) VALUES "11":("n1", 12);
 
 #  In the following example, the insertion fails because "a13" is not int.
@@ -64,8 +64,8 @@ nebula> INSERT VERTEX t2 (name, age) VALUES "13":("n3", 12), "14":("n4", 8);
 ```
 
 ```ngql
-nebula> CREATE TAG t3(p1 int);
-nebula> CREATE TAG t4(p2 string);
+nebula> CREATE TAG IF NOT EXISTS t3(p1 int);
+nebula> CREATE TAG IF NOT EXISTS t4(p2 string);
 
 # The following example inserts vertex "21" with two tags.
 nebula> INSERT VERTEX t3 (p1), t4(p2) VALUES "21": (321, "hello");
@@ -87,7 +87,7 @@ nebula> FETCH PROP ON t2 "11";
 ```
 
 ```ngql
-nebula> CREATE TAG t5(p1 fixed_string(5) NOT NULL, p2 int, p3 int DEFAULT NULL);
+nebula> CREATE TAG IF NOT EXISTS t5(p1 fixed_string(5) NOT NULL, p2 int, p3 int DEFAULT NULL);
 nebula> INSERT VERTEX t5(p1, p2, p3) VALUES "001":("Abe", 2, 3);
 
 # In the following example, the insertion fails because the value of p1 cannot be NULL.

docs-2.0/3.ngql-guide/12.vertex-statements/3.upsert-vertex.md

@@ -105,7 +105,7 @@ nebula> UPSERT VERTEX ON player "player668" \
 In the last query of the preceding examples, since `age` has no default value, when the vertex is created, `age` is `NULL`, and `age = age + 1` does not take effect. But if `age` has a default value, `age = age + 1` will take effect. For example:
 
 ```ngql
-nebula> CREATE TAG player_with_default(name string, age int DEFAULT 20);
+nebula> CREATE TAG IF NOT EXISTS player_with_default(name string, age int DEFAULT 20);
 Execution succeeded
 
 nebula> UPSERT VERTEX ON player_with_default "player101" \

docs-2.0/3.ngql-guide/13.edge-statements/1.insert-edge.md

@@ -45,15 +45,15 @@ INSERT EDGE [IF NOT EXISTS] <edge_type> ( <prop_name_list> ) {VALUES | VALUE}
 
 ```ngql
 # The following example creates edge type e1 with no property and inserts an edge from vertex "10" to vertex "11" with no property.
-nebula> CREATE EDGE e1();                 
+nebula> CREATE EDGE IF NOT EXISTS e1();                 
 nebula> INSERT EDGE e1 () VALUES "10"->"11":();  
 
 # The following example inserts an edge from vertex "10" to vertex "11" with no property. The edge rank is 1.
 nebula> INSERT EDGE e1 () VALUES "10"->"11"@1:(); 
 ```
 
 ```ngql
-nebula> CREATE EDGE e2 (name string, age int); 
+nebula> CREATE EDGE IF NOT EXISTS e2 (name string, age int); 
 nebula> INSERT EDGE e2 (name, age) VALUES "11"->"13":("n1", 1);
 
 # The following example creates edge type e2 with two properties.

docs-2.0/3.ngql-guide/13.edge-statements/3.upsert-edge.md

@@ -106,7 +106,7 @@ nebula> UPSERT EDGE on serve \
 In the last query of the preceding example, since `end_year` has no default value, when the edge is created, `end_year` is `NULL`, and `end_year = end_year + 1` does not take effect. But if `end_year` has a default value, `end_year = end_year + 1` will take effect. For example:
 
 ```ngql
-nebula> CREATE EDGE serve_with_default(start_year int, end_year int DEFAULT 2010);
+nebula> CREATE EDGE IF NOT EXISTS serve_with_default(start_year int, end_year int DEFAULT 2010);
 Execution succeeded
 
 nebula> UPSERT EDGE on serve_with_default \

docs-2.0/3.ngql-guide/14.native-index-statements/1.create-native-index.md

@@ -82,43 +82,43 @@ CREATE {TAG | EDGE} INDEX [IF NOT EXISTS] <index_name> ON {<tag_name> | <edge_na
 ## Create tag/edge type indexes
 
 ```ngql
-nebula> CREATE TAG INDEX player_index on player();
+nebula> CREATE TAG INDEX IF NOT EXISTS player_index on player();
 ```
 
 ```ngql
-nebula> CREATE EDGE INDEX follow_index on follow();
+nebula> CREATE EDGE INDEX IF NOT EXISTS follow_index on follow();
 ```
 
 After indexing a tag or an edge type, you can use the `LOOKUP` statement to retrieve the VID of all vertices `with the tag`, or `the source vertex ID, destination vertex ID, and ranks` of `all edges with the edge type`. For more information, see [LOOKUP](../7.general-query-statements/5.lookup.md).
 
 ## Create single-property indexes
 
 ```ngql
-nebula> CREATE TAG INDEX player_index_0 on player(name(10));
+nebula> CREATE TAG INDEX IF NOT EXISTS player_index_0 on player(name(10));
 ```
 
 The preceding example creates an index for the `name` property on all vertices carrying the `player` tag. This example creates an index using the first 10 characters of the `name` property.
 
 ```ngql
 # To index a variable-length string property, you need to specify the index length.
-nebula> CREATE TAG var_string(p1 string);
-nebula> CREATE TAG INDEX var ON var_string(p1(10));
+nebula> CREATE TAG IF NOT EXISTS var_string(p1 string);
+nebula> CREATE TAG INDEX IF NOT EXISTS var ON var_string(p1(10));
 
 # To index a fixed-length string property, you do not need to specify the index length.
-nebula> CREATE TAG fix_string(p1 FIXED_STRING(10));
-nebula> CREATE TAG INDEX fix ON fix_string(p1);
+nebula> CREATE TAG IF NOT EXISTS fix_string(p1 FIXED_STRING(10));
+nebula> CREATE TAG INDEX IF NOT EXISTS fix ON fix_string(p1);
 ```
 
 ```ngql
-nebula> CREATE EDGE INDEX follow_index_0 on follow(degree);
+nebula> CREATE EDGE INDEX IF NOT EXISTS follow_index_0 on follow(degree);
 ```
 
 ## Create composite property indexes
 
 An index on multiple properties on a tag (or an edge type) is called a composite property index.
 
 ```ngql
-nebula> CREATE TAG INDEX player_index_1 on player(name(10), age);
+nebula> CREATE TAG INDEX IF NOT EXISTS player_index_1 on player(name(10), age);
 ```
 
 !!! caution

docs-2.0/3.ngql-guide/14.native-index-statements/4.rebuild-native-index.md

@@ -24,8 +24,8 @@ REBUILD {TAG | EDGE} INDEX [<index_name_list>];
 ## Examples
 
 ```ngql
-nebula> CREATE TAG person(name string, age int, gender string, email string);
-nebula> CREATE TAG INDEX single_person_index ON person(name(10));
+nebula> CREATE TAG IF NOT EXISTS person(name string, age int, gender string, email string);
+nebula> CREATE TAG INDEX IF NOT EXISTS single_person_index ON person(name(10));
 
 # The following example rebuilds an index and returns the job ID.
 nebula> REBUILD TAG INDEX single_person_index;

docs-2.0/3.ngql-guide/15.full-text-index-statements/1.search-with-text-based-index.md

@@ -74,7 +74,7 @@ LOOKUP ON {<tag> | <edge_type>} WHERE <expression> [YIELD <return_list>];
 
 ```ngql
 // This example creates the graph space.
-nebula> CREATE SPACE basketballplayer (partition_num=3,replica_factor=1, vid_type=fixed_string(30));
+nebula> CREATE SPACE IF NOT EXISTS basketballplayer (partition_num=3,replica_factor=1, vid_type=fixed_string(30));
 
 // This example signs in the text service.
 nebula> SIGN IN TEXT SERVICE (127.0.0.1:9200);
@@ -86,10 +86,10 @@ nebula> USE basketballplayer;
 nebula> ADD LISTENER ELASTICSEARCH 192.168.8.5:9789;
 
 // This example creates the tag.
-nebula> CREATE TAG player(name string, age int);
+nebula> CREATE TAG IF NOT EXISTS player(name string, age int);
 
 // This example creates the native index.
-nebula> CREATE TAG INDEX name ON player(name(20));
+nebula> CREATE TAG INDEX IF NOT EXISTS name ON player(name(20));
 
 // This example rebuilds the native index.
 nebula> REBUILD TAG INDEX;

docs-2.0/3.ngql-guide/16.subgraph-and-path/1.get-subgraph.md

@@ -33,12 +33,12 @@ The following graph is used as the sample.
 Insert the test data:
 
 ```ngql
-nebula> CREATE SPACE subgraph(partition_num=15, replica_factor=1, vid_type=fixed_string(30));
+nebula> CREATE SPACE IF NOT EXISTS subgraph(partition_num=15, replica_factor=1, vid_type=fixed_string(30));
 nebula> USE subgraph;
-nebula> CREATE TAG player(name string, age int);
-nebula> CREATE TAG team(name string);
-nebula> CREATE EDGE follow(degree int);
-nebula> CREATE EDGE serve(start_year int, end_year int);
+nebula> CREATE TAG IF NOT EXISTS player(name string, age int);
+nebula> CREATE TAG IF NOT EXISTS team(name string);
+nebula> CREATE EDGE IF NOT EXISTS follow(degree int);
+nebula> CREATE EDGE IF NOT EXISTS serve(start_year int, end_year int);
 nebula> INSERT VERTEX player(name, age) VALUES "player100":("Tim Duncan", 42);
 nebula> INSERT VERTEX player(name, age) VALUES "player101":("Tony Parker", 36);
 nebula> INSERT VERTEX player(name, age) VALUES "player102":("LaMarcus Aldridge", 33);

docs-2.0/3.ngql-guide/3.data-types/10.geography.md

@@ -28,19 +28,19 @@ For functions about the geography data type, see [Geography functions](../6.func
 
 ```ngql
 //Create a Tag to allow storing any geography data type.
-nebula> CREATE TAG any_shape(geo geography);
+nebula> CREATE TAG IF NOT EXISTS any_shape(geo geography);
 
 //Create a Tag to allow storing a point only.
-nebula> CREATE TAG only_point(geo geography(point));
+nebula> CREATE TAG IF NOT EXISTS only_point(geo geography(point));
 
 //Create a Tag to allow storing a linestring only.
-nebula> CREATE TAG only_linestring(geo geography(linestring));
+nebula> CREATE TAG IF NOT EXISTS only_linestring(geo geography(linestring));
 
 //Create a Tag to allow storing a polygon only.
-nebula> CREATE TAG only_polygon(geo geography(polygon));
+nebula> CREATE TAG IF NOT EXISTS only_polygon(geo geography(polygon));
 
 //Create an Edge type to allow storing any geography data type.
-nebula> CREATE EDGE any_shape_edge(geo geography);
+nebula> CREATE EDGE IF NOT EXISTS any_shape_edge(geo geography);
 
 //Create a vertex to store the geography of a polygon.
 nebula> INSERT VERTEX any_shape(geo) VALUES "103":(ST_GeogFromText("POLYGON((0 1, 1 2, 2 3, 0 1))"));
@@ -65,7 +65,7 @@ nebula> FETCH PROP ON any_shape_edge "201"->"302" YIELD ST_ASText(any_shape_edge
 +---------------------+---------------------+----------------------+---------------------------------+
 
 //Create an index for the geography of the Tag any_shape and run LOOKUP.
-nebula> CREATE TAG INDEX any_shape_geo_index ON any_shape(geo);
+nebula> CREATE TAG INDEX IF NOT EXISTS any_shape_geo_index ON any_shape(geo);
 nebula> REBUILD TAG INDEX any_shape_geo_index;
 nebula> LOOKUP ON any_shape YIELD ST_ASText(any_shape.geo);
 +----------+-------------------------------------------------+

docs-2.0/3.ngql-guide/3.data-types/3.string.md

@@ -24,13 +24,13 @@ For example:
 - Define the data type of the property as a fixed-length string
 
     ```ngql
-    nebula> CREATE TAG t1 (p1 FIXED_STRING(10)); 
+    nebula> CREATE TAG IF NOT EXISTS t1 (p1 FIXED_STRING(10)); 
     ```
 
 - Define the data type of the property as a variable-length string
 
     ```ngql
-    nebula> CREATE TAG t2 (p2 STRING); 
+    nebula> CREATE TAG IF NOT EXISTS t2 (p2 STRING); 
     ```
 
 When the fixed-length string you try to write exceeds the length limit:

docs-2.0/3.ngql-guide/3.data-types/4.date-and-time.md

@@ -78,7 +78,7 @@ The `TIMESTAMP` data type is used for values that contain both date and time par
 1. Create a tag named `date1` with three properties: `DATE`, `TIME`, and `DATETIME`.
 
     ```ngql
-    nebula> CREATE TAG date1(p1 date, p2 time, p3 datetime);
+    nebula> CREATE TAG IF NOT EXISTS date1(p1 date, p2 time, p3 datetime);
     ```
 
 2. Insert a vertex named `test1`.
@@ -90,7 +90,7 @@ The `TIMESTAMP` data type is used for values that contain both date and time par
 3. Return the content of the property `p1` on `test1`.
 
     ```ngql
-    nebula> CREATE TAG INDEX date1_index ON date1(p1);
+    nebula> CREATE TAG INDEX IF NOT EXISTS date1_index ON date1(p1);
     nebula> REBUILD TAG INDEX date1_index;
     nebula> MATCH (v:date1) RETURN v.p1;
     +------------+
@@ -103,7 +103,7 @@ The `TIMESTAMP` data type is used for values that contain both date and time par
 4. Create a tag named `school` with the property of `TIMESTAMP`.
 
     ```ngql
-    nebula> CREATE TAG school(name string , found_time timestamp);
+    nebula> CREATE TAG IF NOT EXISTS school(name string , found_time timestamp);
     ```
 
 5. Insert a vertex named `DUT` with a found-time timestamp of `"1988-03-01T08:00:00"`.