- 在
LOOKUP的文档中，我注意到Limitations of using WHERE in LOOKUP小节中提到了Range scan is not supported in the string-type index.其中的SCAN操作我不太明白，在文档中并没有找到对应部分，可否简单介绍一下呢？ - 我在nebula-python中找到了相关操作，是否
SCAN就是遍历操作？
lookup和scan是两个接口，并没有啥关系。lookup那个就是需要底层去扫描一些数据（但是string在1.0不支持 >, <这些过滤条件，只支持等值，所以你能看到上面的报错）。
好的好的，但是我还有两点疑问：
1、 scan也是一种查询接口，是否有对应的查询语句？还是只在实现的底层使用呢？我还是不明白这个限制在我实际中会有什么影响。
2、 在1.0中不支持，这是2.0的文档，是不是意味着在2.0中并不存在此限制？
我突然想起来，昨天在上一个问题中，explain操作MATCH时，也看到了scan操作，当时就不太清楚，所以这里再仔细问一下 
(root@nebula) [yago]> EXPLAIN format="row" match (v: Person{name: "Donald_Trump"}) return v;
Execution succeeded (time spent 1281/2727 us)
Execution Plan
-----+-------------+--------------+----------------+--------------------------------------------------------------------------------------
| id | name | dependencies | profiling data | operator info |
-----+-------------+--------------+----------------+--------------------------------------------------------------------------------------
| 8 | Project | 7 | | outputVar: [{"colNames":["v"],"name":"__Project_8","type":"DATASET"}] |
| | | | | inputVar: __Filter_7 |
| | | | | columns: ["$v"] |
-----+-------------+--------------+----------------+--------------------------------------------------------------------------------------
| 7 | Filter | 6 | | outputVar: [{"colNames":["v","__COL_0"],"name":"__Filter_7","type":"DATASET"}] |
| | | | | inputVar: __Project_6 |
| | | | | condition: (hasSameEdgeInPath($-.__COL_0)==false) |
-----+-------------+--------------+----------------+--------------------------------------------------------------------------------------
| 6 | Project | 5 | | outputVar: [{"colNames":["v","__COL_0"],"name":"__Project_6","type":"DATASET"}] |
| | | | | inputVar: __Project_5 |
| | | | | columns: ["startNode($-._path) AS v","reversePath(PathBuild[$-._path]) AS __COL_0"] |
-----+-------------+--------------+----------------+--------------------------------------------------------------------------------------
| 5 | Project | 4 | | outputVar: [{"colNames":["_path"],"name":"__Project_5","type":"DATASET"}] |
| | | | | inputVar: __Filter_4 |
| | | | | columns: ["PathBuild[VERTEX]"] |
-----+-------------+--------------+----------------+--------------------------------------------------------------------------------------
| 4 | Filter | 3 | | outputVar: [{"colNames":[],"name":"__Filter_4","type":"DATASET"}] |
| | | | | inputVar: __GetVertices_3 |
| | | | | condition: (VERTEX.name==Donald_Trump) |
-----+-------------+--------------+----------------+--------------------------------------------------------------------------------------
| 3 | GetVertices | 2 | | outputVar: [{"colNames":[],"name":"__GetVertices_3","type":"DATASET"}] |
| | | | | inputVar: __Dedup_2 |
| | | | | space: 1 |
| | | | | dedup: false |
| | | | | limit: 9223372036854775807 |
| | | | | filter: |
| | | | | orderBy: [] |
| | | | | src: $-._vid |
| | | | | props: [] |
| | | | | exprs: [] |
-----+-------------+--------------+----------------+--------------------------------------------------------------------------------------
| 2 | Dedup | 1 | | outputVar: [{"colNames":["_vid"],"name":"__Dedup_2","type":"DATASET"}] |
| | | | | inputVar: __Project_1 |
-----+-------------+--------------+----------------+--------------------------------------------------------------------------------------
| 1 | Project | 11 | | outputVar: [{"colNames":["_vid"],"name":"__Project_1","type":"DATASET"}] |
| | | | | inputVar: __IndexScan_0 |
| | | | | columns: ["$_vid"] |
-----+-------------+--------------+----------------+--------------------------------------------------------------------------------------
| 11 | IndexScan | 10 | | outputVar: [{"colNames":["_vid"],"name":"__IndexScan_0","type":"DATASET"}] |
| | | | | inputVar: |
| | | | | space: 1 |
| | | | | dedup: false |
| | | | | limit: 9223372036854775807 |
| | | | | filter: |
| | | | | orderBy: [] |
| | | | | schemaId: 25 |
| | | | | isEdge: false |
| | | | | returnCols: ["_vid"] |
| | | | | indexCtx: [{"columnHints":[],"index_id":339,"filter":""}] |
-----+-------------+--------------+----------------+--------------------------------------------------------------------------------------
| 10 | Start | | | outputVar: [{"colNames":[],"name":"__Start_10","type":"DATASET"}] |
-----+-------------+--------------+----------------+--------------------------------------------------------------------------------------
Wed, 13 Jan 2021 22:43:19 EST
- scan这个查询接口是用storage client直接连接storage的，一般不会使用
- 是的
- explain看到的IndexScan指的是lookup
好的好的，非常感谢！