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Properties() function reduces query performance #2623

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Properties() function reduces query performance #2623

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properties()-function-reduces-query-performance
abby-cyber Mar 1, 2023
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Update 4.schema.md
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16 changes: 16 additions & 0 deletions docs-2.0/3.ngql-guide/6.functions-and-expressions/4.schema.md
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Expand Up @@ -56,6 +56,18 @@ nebula> LOOKUP ON player WHERE player.age > 45 \
+-------------------------------------+
```

用户也可以使用属性引用符（`$^`和`$$`）替代函数`properties()`中的`vertex`参数来获取点的所有属性。

- `$^`表示探索开始时的点数据。例如`GO FROM "player100" OVER follow reversely YIELD properties($^)`中，`$^`指`player100`这个点。

- `$$`表示探索结束的终点数据。

`properties($^)`和`properties($$)`一般用于`GO`语句中。更多信息，请参见[属性引用符](../5.operators/5.property-reference.md)。

!!! caution

用户可以通过`properties().<property_name>`来获取点的指定属性。但是不建议使用这种方式获取指定属性，因为`properties()`函数返回所有属性，这样会降低查询性能。
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### properties(edge)

properties(edge) 返回边的所有属性。
Expand All @@ -77,6 +89,10 @@ nebula> GO FROM "player100" OVER follow \
+------------------+
```

!!! warning

用户可以通过`properties(edge).<property_name>`来获取边的指定属性。但是不建议使用这种方式获取指定属性，因为`properties(edge)`函数返回边的所有属性，这样会降低查询性能。

### type(edge)

type(edge) 返回边的 Edge type。
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