UPSERT EDGE

UPSERT EDGE语句结合UPDATE和INSERT，如果边存在，会更新边的属性；如果边不存在，会插入新的边。

备注

UPSERT EDGE语句一次只能修改一个 Edge type 的属性。

UPSERT EDGE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。

危险

在高并发场景下，不要使用UPSERT语句。可以使用UPDATE或INSERT语句代替。

语法

UPSERT EDGE ON <edge_type>
<src_vid> -> <dst_vid> [@rank]
SET <update_prop>
[WHEN <condition>]
[YIELD <properties>]

参数	是否必须	说明	示例
ON <edge_type>	是	指定 Edge type。要修改的属性必须在这个 Edge type 内。	ON serve
<src_vid>	是	指定边的起始点 ID。	"player100"
<dst_vid>	是	指定边的目的点 ID。	"team204"
<rank>	否	指定边的 rank 值。数据类型为int。	10
SET <update_prop>	是	指定如何修改属性值。	SET start_year = start_year +1
WHEN <condition>	否	指定过滤条件。	WHEN end_year < 2010
YIELD <output>	否	指定语句的输出格式。	YIELD start_year AS Start_Year

插入不存在的边

如果边不存在，无论WHEN子句的条件是否满足，都会插入边，同时执行SET子句，因此新插入的边的属性值取决于：

• SET子句。

• 属性是否有默认值。

例如：

• 要插入的边包含基于 Edge typeserve的属性start_year和end_year。

• SET子句指定end_year = 2021。

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	start_year属性值	end_year属性值
是	是	默认值	2021
是	否	NULL	2021
否	是	默认值	2021
否	否	NULL	2021

示例如下：

// 查看如下三个点是否有 serve 类型的出边，结果 “Empty set” 表示没有 serve 类型的出边。
nebula> GO FROM "player666", "player667", "player668" \
        OVER serve \
        YIELD properties(edge).start_year, properties(edge).end_year;
+-----------------------------+---------------------------+
| properties(EDGE).start_year | properties(EDGE).end_year |
+-----------------------------+---------------------------+
+-----------------------------+---------------------------+
Empty set

nebula> UPSERT EDGE on serve \
        "player666" -> "team200"@0 \
        SET end_year = 2021 \
        WHEN end_year == 2010 \
        YIELD start_year, end_year;
+------------+----------+
| start_year | end_year |
+------------+----------+
| __NULL__   | 2021     |
+------------+----------+

nebula> UPSERT EDGE on serve \
        "player666" -> "team200"@0 \
        SET end_year = 2022 \
        WHEN end_year == 2010 \
        YIELD start_year, end_year;
+------------+----------+
| start_year | end_year |
+------------+----------+
| __NULL__   | 2021     |
+------------+----------+

nebula> UPSERT EDGE on serve \
        "player667" -> "team200"@0 \
        SET end_year = 2022 \
        YIELD start_year, end_year;
+------------+----------+
| start_year | end_year |
+------------+----------+
| __NULL__   | 2022     |
+------------+----------+

nebula> UPSERT EDGE on serve \
        "player668" -> "team200"@0 \
        SET start_year = 2000, end_year = end_year + 1 \
        YIELD start_year, end_year;
+------------+----------+
| start_year | end_year |
+------------+----------+
| 2000       | __NULL__ |
+------------+----------+

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

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 \
        "player668" -> "team200" \
        SET end_year = end_year + 1 \
        YIELD start_year, end_year;
+------------+----------+
| start_year | end_year |
+------------+----------+
| __NULL__   | 2011     |
+------------+----------+

修改存在的边

如果边存在，且满足WHEN子句的条件，就会修改边的属性值。

nebula> MATCH (v:player{name:"Ben Simmons"})-[e:serve]-(v2) \
        RETURN e;
+-----------------------------------------------------------------------+
| e                                                                     |
+-----------------------------------------------------------------------+
| [:serve "player149"->"team219" @0 {end_year: 2019, start_year: 2016}] |
+-----------------------------------------------------------------------+

nebula> UPSERT EDGE on serve \
        "player149" -> "team219" \
        SET end_year = end_year + 1 \
        WHEN start_year == 2016 \
        YIELD start_year, end_year;
+------------+----------+
| start_year | end_year |
+------------+----------+
| 2016       | 2020     |
+------------+----------+

如果边存在，但是不满足WHEN子句的条件，修改不会生效。

nebula> MATCH (v:player{name:"Ben Simmons"})-[e:serve]-(v2) \
        RETURN e;
+-----------------------------------------------------------------------+
| e                                                                     |
+-----------------------------------------------------------------------+
| [:serve "player149"->"team219" @0 {end_year: 2020, start_year: 2016}] |
+-----------------------------------------------------------------------+

nebula> UPSERT EDGE on serve \
        "player149" -> "team219" \
        SET end_year = end_year + 1 \
        WHEN start_year != 2016 \
        YIELD start_year, end_year;
+------------+----------+
| start_year | end_year |
+------------+----------+
| 2016       | 2020     |
+------------+----------+