support SELECT FROM TABLESAMPLE syntax #1071
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kennytm
reviewed
Oct 28, 2020
parser.y
Outdated
| @@ -7280,6 +7291,74 @@ SelectStmtFromTable: | |||
| $$ = st | |||
| } | |||
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| SelectStmtFromTableSample: | |||
| SelectStmtBasic "FROM" TableName PartitionNameListOpt TableAsNameOpt "TABLESAMPLE" TableSampleMethodOpt '(' Expression TableSampleUnitOpt ')' RepeatableOpt WhereClauseOptional | |||
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it's better attach this to this line to support JOIN:
TableFactor:
TableName PartitionNameListOpt TableAsNameOpt IndexHintListOpt TableSampleOpt # <--this means the TableSample is part of the ast.TableSource or ast.TableName.
their use in UPDATE and DELETE can be rejected after parsing.
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LGTM |
AilinKid
reviewed
Nov 10, 2020
| @@ -7805,11 +7888,14 @@ TableRef: | |||
| | JoinTable | |||
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| TableFactor: | |||
| TableName PartitionNameListOpt TableAsNameOpt IndexHintListOpt | |||
| TableName PartitionNameListOpt TableAsNameOpt IndexHintListOpt TableSampleOpt | |||
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should append a warning? since we don't support them all in TiDB actually...
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Related work is done in TiDB.
ti-srebot
approved these changes
Nov 10, 2020
tiancaiamao
pushed a commit
to tiancaiamao/parser
that referenced
this pull request
Apr 27, 2021
* support SELECT FROM TABLESAMPLE syntax * refine naming * make table sample clause as a part of TableFactor * address comment
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What problem does this PR solve?
See pingcap/tidb#20567.
What is changed and how it works?
The syntax for "TABLESAMPLE" is as follows:
I putSampleClauseas a special part of rule inSelectStmtinstead ofTableRef, becauseTableRefis also used inUPDATE/DELETEstatements and we don't want to supportTABLESAMPLEfor them.However, this also prevent theJOINclause to be syntax-checked:Check List
Tests
Code changes
N/A
Side effects
N/A
Related changes
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