In the match statement, the where condition may generate unnecessary storage queries

[cangfengzhs]

(root@nebula) [test]> create tag index t_name_index on t(name(8));
(root@nebula) [test]> insert tag t(name) values 1:("a");
(root@nebula) [test]> match (v:t) where v.name=="a" return v;  // a
+-------------------+
| v                 |
+-------------------+
| (1 :t{name: "a"}) |
+-------------------+
Got 1 rows (time spent 14400/15023 us)

Tue, 02 Nov 2021 18:31:53 CST

(root@nebula) [test]> match (v:t) where v.name== -2233785415175766016 return v; // b
+---+
| v |
+---+
+---+
Empty set (time spent 14978/15568 us)

Tue, 02 Nov 2021 18:32:00 CST

Statement a and b will generate request to storage and get the same response. Because encode of "a" and -2233785415175766016 is same in indexKey and there is not value type verify.
However, according to the code given above, we find that the result is different. According to the profile statement, a filter node is actually added to the execution plan and filtered again according to the condition.

(root@nebula) [test]> profile match (v:t) where v.name == -2233785415175766016 return v;
+---+
| v |
+---+
+---+
Empty set (time spent 14035/14819 us)

Execution Plan (optimize time 4289 us)

-----+-------------+--------------+-------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------
| id | name        | dependencies | profiling data                                                                                        | operator info                                                                     |
-----+-------------+--------------+-------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------
| 10 | Project     | 13           | ver: 0, rows: 0, execTime: 48us, totalTime: 52us                                                      | outputVar: [                                                                      |
|    |             |              |                                                                                                       |   {                                                                               |
|    |             |              |                                                                                                       |     "colNames": [                                                                 |
|    |             |              |                                                                                                       |       "v"                                                                         |
|    |             |              |                                                                                                       |     ],                                                                            |
|    |             |              |                                                                                                       |     "name": "__Project_10",                                                       |
|    |             |              |                                                                                                       |     "type": "DATASET"                                                             |
|    |             |              |                                                                                                       |   }                                                                               |
|    |             |              |                                                                                                       | ]                                                                                 |
|    |             |              |                                                                                                       | inputVar: __Filter_9                                                              |
|    |             |              |                                                                                                       | columns: [                                                                        |
|    |             |              |                                                                                                       |   "$v"                                                                            |
|    |             |              |                                                                                                       | ]                                                                                 |
-----+-------------+--------------+-------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------
| 13 | Filter      | 7            | ver: 0, rows: 0, execTime: 41us, totalTime: 45us                                                      | outputVar: [                                                                      |
|    |             |              |                                                                                                       |   {                                                                               |
|    |             |              |                                                                                                       |     "colNames": [                                                                 |
|    |             |              |                                                                                                       |       "v",                                                                        |
|    |             |              |                                                                                                       |       "__COL_0"                                                                   |
|    |             |              |                                                                                                       |     ],                                                                            |
|    |             |              |                                                                                                       |     "name": "__Filter_9",                                                         |
|    |             |              |                                                                                                       |     "type": "DATASET"                                                             |
|    |             |              |                                                                                                       |   }                                                                               |
|    |             |              |                                                                                                       | ]                                                                                 |
|    |             |              |                                                                                                       | inputVar: __Project_7                                                             |
|    |             |              |                                                                                                       | condition: (($v.name==-2233785415175766016) AND !(hasSameEdgeInPath($-.__COL_0))) |
|    |             |              |                                                                                                       | isStable: false                                                                   |
-----+-------------+--------------+-------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------
|  7 | Project     | 6            | ver: 0, rows: 1, execTime: 137us, totalTime: 142us                                                    | outputVar: [                                                                      |
|    |             |              |                                                                                                       |   {                                                                               |
|    |             |              |                                                                                                       |     "colNames": [                                                                 |
|    |             |              |                                                                                                       |       "v",                                                                        |
|    |             |              |                                                                                                       |       "__COL_0"                                                                   |
|    |             |              |                                                                                                       |     ],                                                                            |
|    |             |              |                                                                                                       |     "name": "__Project_7",                                                        |
|    |             |              |                                                                                                       |     "type": "DATASET"                                                             |
|    |             |              |                                                                                                       |   }                                                                               |
|    |             |              |                                                                                                       | ]                                                                                 |
|    |             |              |                                                                                                       | inputVar: __Project_6                                                             |
|    |             |              |                                                                                                       | columns: [                                                                        |
|    |             |              |                                                                                                       |   "startNode($-._path) AS v",                                                     |
|    |             |              |                                                                                                       |   "reversePath(PathBuild[$-._path]) AS __COL_0"                                   |
|    |             |              |                                                                                                       | ]                                                                                 |
-----+-------------+--------------+-------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------
|  6 | Project     | 5            | ver: 0, rows: 1, execTime: 109us, totalTime: 115us                                                    | outputVar: [                                                                      |
|    |             |              |                                                                                                       |   {                                                                               |
|    |             |              |                                                                                                       |     "colNames": [                                                                 |
|    |             |              |                                                                                                       |       "_path"                                                                     |
|    |             |              |                                                                                                       |     ],                                                                            |
|    |             |              |                                                                                                       |     "name": "__Project_6",                                                        |
|    |             |              |                                                                                                       |     "type": "DATASET"                                                             |
|    |             |              |                                                                                                       |   }                                                                               |
|    |             |              |                                                                                                       | ]                                                                                 |
|    |             |              |                                                                                                       | inputVar: __Filter_5                                                              |
|    |             |              |                                                                                                       | columns: [                                                                        |
|    |             |              |                                                                                                       |   "PathBuild[VERTEX]"                                                             |
|    |             |              |                                                                                                       | ]                                                                                 |
-----+-------------+--------------+-------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------
|  5 | Filter      | 16           | ver: 0, **rows: 1,** execTime: 145us, totalTime: 151us                                                    | outputVar: [                                                                      |
|    |             |              |                                                                                                       |   {                                                                               |
|    |             |              |                                                                                                       |     "colNames": [],                                                               |
|    |             |              |                                                                                                       |     "name": "__Filter_5",                                                         |
|    |             |              |                                                                                                       |     "type": "DATASET"                                                             |
|    |             |              |                                                                                                       |   }                                                                               |
|    |             |              |                                                                                                       | ]                                                                                 |
|    |             |              |                                                                                                       | inputVar: __GetVertices_4                                                         |
|    |             |              |                                                                                                       | condition: ("t" IN tags(VERTEX))                                                  |
|    |             |              |                                                                                                       | isStable: false                                                                   |
-----+-------------+--------------+-------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------
| 16 | GetVertices | 11           | {                                                                                                     | outputVar: [                                                                      |
|    |             |              | ver: 0, **rows: 1**, execTime: 351us, totalTime: 1296us                                                   |   {                                                                               |
|    |             |              | "127.0.0.1":9381 exec/total: 290(us)/867(us)                                                          |     "colNames": [],                                                               |
|    |             |              | total_rpc: 1168(us)                                                                                   |     "name": "__GetVertices_4",                                                    |
|    |             |              | }                                                                                                     |     "type": "DATASET"                                                             |
|    |             |              |                                                                                                       |   }                                                                               |
|    |             |              |                                                                                                       | ]                                                                                 |
|    |             |              |                                                                                                       | inputVar: __IndexScan_1                                                           |
|    |             |              |                                                                                                       | space: 4                                                                          |
|    |             |              |                                                                                                       | dedup: true                                                                       |
|    |             |              |                                                                                                       | limit: 9223372036854775807                                                        |
|    |             |              |                                                                                                       | filter:                                                                           |
|    |             |              |                                                                                                       | orderBy: []                                                                       |
|    |             |              |                                                                                                       | src: $_vid                                                                        |
|    |             |              |                                                                                                       | props: [                                                                          |
|    |             |              |                                                                                                       |   {                                                                               |
|    |             |              |                                                                                                       |     "tagId": 5,                                                                   |
|    |             |              |                                                                                                       |     "props": [                                                                    |
|    |             |              |                                                                                                       |       "name",                                                                     |
|    |             |              |                                                                                                       |       "_tag"                                                                      |
|    |             |              |                                                                                                       |     ]                                                                             |
|    |             |              |                                                                                                       |   }                                                                               |
|    |             |              |                                                                                                       | ]                                                                                 |
|    |             |              |                                                                                                       | exprs:                                                                            |
-----+-------------+--------------+-------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------
| 11 | IndexScan   | 0            | {                                                                                                     | outputVar: [                                                                      |
|    |             |              | ver: 0, **rows: 1,** execTime: 0us, totalTime: 5964us                                                     |   {                                                                               |
|    |             |              | storage_detail: {DedupNode:4026(us),IndexOpuputNode:3906(us),IndexScanNode:3654(us),RelNode:4047(us)} |     "colNames": [                                                                 |
|    |             |              | "127.0.0.1":9381 exec/total: 4611(us)/5573(us)                                                        |       "_vid"                                                                      |
|    |             |              | }                                                                                                     |     ],                                                                            |
|    |             |              |                                                                                                       |     "name": "__IndexScan_1",                                                      |
|    |             |              |                                                                                                       |     "type": "DATASET"                                                             |
|    |             |              |                                                                                                       |   }                                                                               |
|    |             |              |                                                                                                       | ]                                                                                 |
|    |             |              |                                                                                                       | inputVar: __VAR_0                                                                 |
|    |             |              |                                                                                                       | space: 4                                                                          |
|    |             |              |                                                                                                       | dedup: false                                                                      |
|    |             |              |                                                                                                       | limit: 9223372036854775807                                                        |
|    |             |              |                                                                                                       | filter:                                                                           |
|    |             |              |                                                                                                       | orderBy: []                                                                       |
|    |             |              |                                                                                                       | schemaId: 5                                                                       |
|    |             |              |                                                                                                       | isEdge: false                                                                     |
|    |             |              |                                                                                                       | returnCols: [                                                                     |
|    |             |              |                                                                                                       |   "_vid"                                                                          |
|    |             |              |                                                                                                       | ]                                                                                 |
|    |             |              |                                                                                                       | indexCtx: [                                                                       |
|    |             |              |                                                                                                       |   {                                                                               |
|    |             |              |                                                                                                       |     "columnHints": [                                                              |
|    |             |              |                                                                                                       |       {                                                                           |
|    |             |              |                                                                                                       |         "beginValue": "-2233785415175766016",                                     |
|    |             |              |                                                                                                       |         "endValue": "__EMPTY__",                                                  |
|    |             |              |                                                                                                       |         "column": "name",                                                         |
|    |             |              |                                                                                                       |         "scanType": "PREFIX"                                                      |
|    |             |              |                                                                                                       |       }                                                                           |
|    |             |              |                                                                                                       |     ],                                                                            |
|    |             |              |                                                                                                       |     "index_id": 6,                                                                |
|    |             |              |                                                                                                       |     "filter": ""                                                                  |
|    |             |              |                                                                                                       |   }                                                                               |
|    |             |              |                                                                                                       | ]                                                                                 |
-----+-------------+--------------+-------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------
|  0 | Start       |              | ver: 0, rows: 0, execTime: 3us, totalTime: 27us                                                       | outputVar: [                                                                      |
|    |             |              |                                                                                                       |   {                                                                               |
|    |             |              |                                                                                                       |     "colNames": [],                                                               |
|    |             |              |                                                                                                       |     "name": "__Start_0",                                                          |
|    |             |              |                                                                                                       |     "type": "DATASET"                                                             |
|    |             |              |                                                                                                       |   }                                                                               |
|    |             |              |                                                                                                       | ]                                                                                 |
-----+-------------+--------------+-------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------

Tue, 02 Nov 2021 18:34:42 CST

So, there are some questions

1. In the match statement, we can compare values between different types (only ==). But there is no type conversion, so the result of the expression is always false. If we want to support the comparison of weak data types, like sql, "1"==1 is true, then our current logic is not correct. If we need a comparison of strong data types, then "1"==1 will always return false, which is meaningless. The query results can be known during query optimization.The current processing logic will only waste CPU resources
2. If we want to implement the comparison of weak data types, then it should not be limited to ==, it should also support comparison operations such as <, >, but currently it is not supported.
3. In this case, the expressions are all used for index optimization, so it is not necessary to perform another filter after selecting the index (if the logic we implemented is correct)

[cangfengzhs]

This looks like a few errors superimposed together and ultimately ensure the correct query results.

[czpmango]

If we want to support the comparison of weak data types, like sql, "1"==1 is true, then our current logic is not correct.

"1"==1 is true in sql but false in cypher. Our current logic of expression is consistent with cypher and the index logic related should be consistent. IMHO, This is just the behavior of the expression, and the implementation of other modules should be delegated to it. More detail please refer to cypher standand.

[Shylock-Hg]

In my mind, index scan which transformed from filter expression should keep the origin semantic of expression.

[CPWstatic]

This would not be fixed at present due to the syntax matter of openCypher.