tidb-functions: add info about special start_key/end_key values (#6728)

[ti-chi-bot]

This is an automated cherry-pick of #6728

What is changed, added or deleted? (Required)

sql> SELECT TABLE_NAME, REGION_ID, START_KEY, END_KEY FROM information_schema.TIKV_REGION_STATUS WHERE TABLE_NAME='stock' AND IS_INDEX=0;
+------------+-----------+--------------------------------------------------------+--------------------------------------------------------+
| TABLE_NAME | REGION_ID | START_KEY                                              | END_KEY                                                |
+------------+-----------+--------------------------------------------------------+--------------------------------------------------------+
| stock      |        74 | 7480000000000000FF4700000000000000F8                   | 7480000000000000FF475F728000000000FF029DF00000000000FA |
| stock      |        72 | 7480000000000000FF475F728000000000FF0D7ECA0000000000FA | 7480000000000000FF4900000000000000F8                   |
| stock      |        78 | 7480000000000000FF475F728000000000FF063E890000000000FA | 7480000000000000FF475F728000000000FF09E0350000000000FA |
| stock      |        76 | 7480000000000000FF475F728000000000FF029DF00000000000FA | 7480000000000000FF475F728000000000FF063E890000000000FA |
| stock      |        80 | 7480000000000000FF475F728000000000FF09E0350000000000FA | 7480000000000000FF475F728000000000FF0D7ECA0000000000FA |
+------------+-----------+--------------------------------------------------------+--------------------------------------------------------+
5 rows in set (0.0144 sec)

sql> SELECT TIDB_DECODE_KEY('7480000000000000FF4700000000000000F8');
+---------------------------------------------------------+
| TIDB_DECODE_KEY('7480000000000000FF4700000000000000F8') |
+---------------------------------------------------------+
| 7480000000000000FF4700000000000000F8                    |
+---------------------------------------------------------+
1 row in set, 1 warning (0.0013 sec)
Warning (code 1105): invalid record/index key: 748000000000000047

sql> SELECT TIDB_DECODE_KEY('7480000000000000FF475F728000000000FF0D7ECA0000000000FA');
+---------------------------------------------------------------------------+
| TIDB_DECODE_KEY('7480000000000000FF475F728000000000FF0D7ECA0000000000FA') |
+---------------------------------------------------------------------------+
| {"_tidb_rowid":884426,"table_id":"71"}                                    |
+---------------------------------------------------------------------------+
1 row in set (0.0013 sec)

sql> SELECT TABLE_NAME, REGION_ID, TIDB_DECODE_KEY(START_KEY) sk, TIDB_DECODE_KEY(END_KEY) ek FROM information_schema.TIKV_REGION_STATUS WHERE TABLE_NAME='stock' AND IS_INDEX=0 ORDER BY IF(JSON_VALID(sk),sk->'$."_tidb_rowid"',0);
+------------+-----------+----------------------------------------+----------------------------------------+
| TABLE_NAME | REGION_ID | sk                                     | ek                                     |
+------------+-----------+----------------------------------------+----------------------------------------+
| stock      |        74 | 7480000000000000FF4700000000000000F8   | {"_tidb_rowid":171504,"table_id":"71"} |
| stock      |        76 | {"_tidb_rowid":171504,"table_id":"71"} | {"_tidb_rowid":409225,"table_id":"71"} |
| stock      |        78 | {"_tidb_rowid":409225,"table_id":"71"} | {"_tidb_rowid":647221,"table_id":"71"} |
| stock      |        80 | {"_tidb_rowid":647221,"table_id":"71"} | {"_tidb_rowid":884426,"table_id":"71"} |
| stock      |        72 | {"_tidb_rowid":884426,"table_id":"71"} | 7480000000000000FF4900000000000000F8   |
+------------+-----------+----------------------------------------+----------------------------------------+
5 rows in set, 2 warnings (0.0133 sec)
Warning (code 1105): invalid record/index key: 748000000000000047
Warning (code 1105): invalid record/index key: 748000000000000049

Which TiDB version(s) do your changes apply to? (Required)

• master (the latest development version)
• v5.4 (TiDB 5.4 versions)
• v5.3 (TiDB 5.3 versions)
• v5.2 (TiDB 5.2 versions)
• v5.1 (TiDB 5.1 versions)
• v5.0 (TiDB 5.0 versions)
• v4.0 (TiDB 4.0 versions)
• v3.1 (TiDB 3.1 versions)
• v3.0 (TiDB 3.0 versions)
• v2.1 (TiDB 2.1 versions)

[Oreoxmt]

/approve

[ti-chi-bot]

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[Oreoxmt]

/verify