如何用ApacheAGE在单条查询中返回不同图的顶点？

已创建family_tree和taxonomy_biology两个图，想要一次性获取这两个图的所有顶点，执行了以下查询：

SELECT * FROM cypher ('family_tree' AND 'taxonomy_biology', $$
MATCH (v)
RETURN v
$$) as (vertex agtype);

终端返回错误：

ERROR:  invalid input syntax for type boolean: "family_tree"
LINE 1: SELECT * FROM cypher('family_tree' AND 'taxonomy_biology', $...

单独查询每个图时可以正常返回顶点：
查询taxonomy_biology：

SELECT * FROM cypher('taxonomy_biology', $$
MATCH (v)
RETURN v
$$) as (VERTEX agtype);

结果：

vertex
-----------------------------------------------------------------------------------------
 {"id": 844424930131969, "label": "Kingdom", "properties": {"name": "Animalia"}}::vertex
 {"id": 1125899906842625, "label": "Phylum", "properties": {"name": "Cnidaria"}}::vertex
(2 rows)

查询family_tree：

SELECT * FROM cypher('family_tree', $$                                                                                                                     
MATCH (v)
RETURN v
$$) as (VERTEX agtype);

结果：

vertex

---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
 {"id": 844424930131969, "label": "Person", "properties": {"name": "Louis", "titles": ["Emperor of the Carolingian Empire", "King of the Franks", "King of Aquitaine"], "year_born": 778, "year_died": 840}}::vertex
 {"id": 844424930131970, "label": "Person", "properties": {"name": "Hildegard", "titles": ["Frankish queen consort"], "year_born": 754, "year_died": 783}}::vertex
 {"id": 844424930131971, "label": "Person", "properties": {"name": "Charlemagne", "titles": ["Holy Roman Emperor", "King of the Franks", "King of the Lombards"], "year_born": 747, "year_died": 814}}::vertex
(3 rows)

解决方案 #

Apache AGE的cypher()函数第一个参数仅支持传入单个图名，无法通过AND直接指定多个图。要在单条查询中获取多个图的所有顶点，需要使用UNION ALL将两个单独的查询结果合并：

SELECT * FROM cypher('taxonomy_biology', $$
MATCH (v)
RETURN v
$$) as (vertex agtype)
UNION ALL
SELECT * FROM cypher('family_tree', $$
MATCH (v)
RETURN v
$$) as (vertex agtype);

• 使用UNION ALL会保留所有结果（包括可能存在的ID重复的顶点）；如果需要去重（比如两个图中存在完全相同的顶点），可以替换为UNION，但UNION会对结果集去重，性能略低。

内容的提问来源于stack exchange，提问作者Matheus Farias