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UPSERT VERTEX

UPSERT VERTEX语句结合UPDATEINSERT,如果点存在,会修改点的属性值;如果点不存在,会插入新的点。

Note

UPSERT VERTEX一次只能修改一个标签。

UPSERT VERTEX性能远低于INSERT,因为UPSERT是一组分片级别的读取、修改、写入操作。

Danger

禁止在高并发写操作的情况下使用UPSERT语句,请使用UPDATEINSERT代替。

语法

UPSERT VERTEX ON <tag> <vid>
SET <update_prop>
[WHEN <condition>]
[YIELD <output>]
参数 是否必须 说明 示例
ON <tag> 指定点的标签。要修改的属性必须在这个标签内。 ON player
<vid> 指定要修改或插入的点ID。 "player100"
SET <update_prop> 指定如何修改属性值。 SET age = age +1
WHEN <condition> 指定过滤条件。 WHEN name == "Tim"
YIELD <output> 指定语句的输出格式。 YIELD name AS Name

插入不存在的点

如果点不存在,无论WHEN子句的条件是否满足,都会插入点,同时执行SET子句,因此新插入的点的属性值取决于:

  • SET子句。
  • 属性是否有默认值。

例如:

  • 要插入的点包含基于标签player的属性nameage
  • SET子句指定age=30

不同情况下的属性值如下表。

是否满足WHEN子句条件 属性是否有默认值 name属性值 age属性值
默认值 30
NULL 30
默认值 30
NULL 30

示例如下:

// 查看三个点是否存在,结果“Empty set”表示顶点不存在。
nebula> FETCH PROP ON * "player666", "player667", "player668";
Empty set

nebula> UPSERT VERTEX ON player "player666" \
        SET age = 30 \
        WHEN name == "Joe" \
        YIELD name AS Name, age AS Age;
+----------+----------+
| Name     | Age      |
+----------+----------+
| __NULL__ | 30       |
+----------+----------+

nebula> UPSERT VERTEX ON player "player666" SET age = 31 WHEN name == "Joe" YIELD name AS Name, age AS Age;
+----------+-----+
| Name     | Age |
+----------+-----+
| __NULL__ | 30  |
+----------+-----+

nebula> UPSERT VERTEX ON player "player667" \
        SET age = 31 \
        YIELD name AS Name, age AS Age;
+----------+-----+
| Name     | Age |
+----------+-----+
| __NULL__ | 31  |
+----------+-----+

nebula> UPSERT VERTEX ON player "player668" \
        SET name = "Amber", age = age + 1 \
        YIELD name AS Name, age AS Age;
+---------+----------+
| Name    | Age      |
+---------+----------+
| "Amber" | __NULL__ |
+---------+----------+

上面最后一个示例中,因为age没有默认值,插入点时,age默认值为NULL,执行age = age + 1后仍为NULL。如果age有默认值,则age = age + 1可以正常执行,例如:

nebula> CREATE TAG player_with_default(name string, age int DEFAULT 20);
Execution succeeded

nebula> UPSERT VERTEX ON player_with_default "player101" \
        SET age = age + 1 \
        YIELD name AS Name, age AS Age;

+----------+-----+
| Name     | Age |
+----------+-----+
| __NULL__ | 21  |
+----------+-----+

修改存在的点

如果点存在,且满足WHEN子句的条件,就会修改点的属性值。

nebula> FETCH PROP ON player "player101";
+-----------------------------------------------------+
| vertices_                                           |
+-----------------------------------------------------+
| ("player101" :player{age: 42, name: "Tony Parker"}) |
+-----------------------------------------------------+

nebula> UPSERT VERTEX ON player "player101" \
        SET age = age + 2 \
        WHEN name == "Tony Parker" \
        YIELD name AS Name, age AS Age;
+---------------+-----+
| Name          | Age |
+---------------+-----+
| "Tony Parker" | 44  |
+---------------+-----+

如果点存在,但是不满足WHEN子句的条件,修改不会生效。

nebula> FETCH PROP ON player "player101";
+-----------------------------------------------------+
| vertices_                                           |
+-----------------------------------------------------+
| ("player101" :player{age: 44, name: "Tony Parker"}) |
+-----------------------------------------------------+

nebula> UPSERT VERTEX ON player "player101" \
        SET age = age + 2 \
        WHEN name == "Someone else" \
        YIELD name AS Name, age AS Age;
+---------------+-----+
| Name          | Age |
+---------------+-----+
| "Tony Parker" | 44  |
+---------------+-----+

最后更新: 2021年5月10日