Remove parenthesis from the AST #5906
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This was referenced Mar 9, 2020
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go/vt/sqlparser/tracked_buffer.go
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| case 'a': | ||
| buf.WriteArg(values[fieldnum].(string)) | ||
| case 'p': |
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This part feels like it can lead to future bugs. Is there a way to make %v handle this correctly?
The main concern is this: someone may call Myprintf with %v without knowing that they should have called ExprPrintf with %p.
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@sougou I've squashed, rebased and generally cleaned up this PR Is there anything else you think needs to change before we can merge it? |
Instead of keeping this information in the AST, we put in parens in the string representation of queries when needed when printing. This includes adding code that takes precendence into consideration - something that already we already need to do when parsing. Unfortunately I haven't found a good way to use the same source information for both sides of the precedence puzzle. Signed-off-by: Andres Taylor <andres@planetscale.com>
Myprintf uses from AST now include the parent struct. In order to get better readability and guarantees that we don't introduce regressions in the future, this refactoring changes Myprintf uses from the AST to always provide the parent structure. Using this information, Myprintf can figure out when parens are needed. Signed-off-by: Harshit Gangal <harshit@planetscale.com> Signed-off-by: Andres Taylor <andres@planetscale.com>
Signed-off-by: Andres Taylor <andres@planetscale.com>
Signed-off-by: Andres Taylor <andres@planetscale.com>
sougou
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Mar 27, 2020
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To make sure that the meaning of queries didn't change by mistake, Vitess used to keep parens around in the AST even though they are nog strictly speaking needed there.
This change set solves the parens problem by taking precedence into consideration, and adding parens to the output string when needed instead of keeping them in the AST structure.
The benefit is that other parts of the code can just ignore parenthesis and trust that the AST will handle it for them.
NOTE: This introduces a behaviour change that can be noticable for end-users. Unaliased SELECT expressions can get the column name used changed (by parens being removed).
Example:
Vitess already did some changing of column names (white spaces were not kept around). Now it does it a little differently. If you need a specific name, it's advisable to use the
AS columnAliasconstruct.