agens-graph - 如何在 AgensGraph 上获取数组的标签？

Question

我试图在 AgensGraph 上获取数组标签？

但是，它返回关于类型转换的错误。

我怎样才能得到数组的标签？

agens=# match (n:o) with collect(n) as n return labels(n[0]);
ERROR:  cannot cast type jsonb to vertex
agens =# match (n:o{id:1}) return labels(n);
 labels 
--------
 ["o"]
(1 row)

Answer 1

There is a problem on array processing of AgensGraph.

function "collect" converts all data-types to json.

And It is impossible to revert data-types.

agens =# match (n:o) with collect(n) as n return n[0];
                           n                            
--------------------------------------------------------
 {"id": "3.1", "tid": "(0,1)", "properties": {"id": 1}}
(1 row)

agens =# match (n:o{id:1}) return n;
        n        
-----------------
 o[3.1]{"id": 1}
(1 row)

Use "array_agg" instead of "collect".

agens =# match (n:o) with array_agg(n) as n return n[0];
        n        
-----------------
 o[3.1]{"id": 1}
(1 row)

agens =# match (n:o) with array_agg(n) as n return labels(n[0]);
 labels 
--------
 ["o"]
(1 row)