*: support default expression value for sequence #14589
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ghost
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AilinKid
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table/column.go
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| var defaultExpr ast.ExprNode | ||
| expr := fmt.Sprintf("select %s", x) | ||
| charset, collation := charset.GetDefaultCharsetAndCollate() | ||
| stmts, _, err := parser.New().Parse(expr, charset, collation) |
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It is enough to pass empty strings to charset and collation.
A question: is it necessary to parse the expression once again?
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- nice idea.
- Actually we can do the expr cache like
colDefaultValsdoes, Given the sequence function hasn't been implemented now, it's hard to do the test, so I push it to the next PR.
table/column.go
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| var defaultExpr ast.ExprNode | ||
| expr := fmt.Sprintf("select %s", x) | ||
| charset, collation := charset.GetDefaultCharsetAndCollate() | ||
| stmts, _, err := parser.New().Parse(expr, charset, collation) |
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- nice idea.
- Actually we can do the expr cache like
colDefaultValsdoes, Given the sequence function hasn't been implemented now, it's hard to do the test, so I push it to the next PR.
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/rebuild |
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/build |
| Value: types.NewDatum(v.Name.L), | ||
| RetType: types.NewFieldType(mysql.TypeString), | ||
| } | ||
| er.ctxStackAppend(val, types.EmptyName) |
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Does any place use this element in the stack?
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only nextval / lastval / setval function will take it as string arg. (this function will be added in next pr)
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Should we guarantee the stack empty at the end of the rewrite stage? If we should, does this element break our guarantee?
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yes we can, take nextval(tableName) for example, tableName will be rewritten as a constant string, then the upper FuncCallExpr will consume it.
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/run-unit-test |
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/merge |
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What problem does this PR solve?
linked Parser PR: #731
Problem 1:
before this pr, when we create a table with sequence's next value as it's default value like
will get a crash on expression rewrite.
Problem 2:
In some cases, the default value is dynamic, needing to be evaluated every time be called.
Problem 3:
Now, the static default value will be cache in the case like
insert into t values (),(),()....What is changed and how it works?
1: rewrite the tableName (specified sequence to constant string args)
2: store the expr_string in default value as the generated column does.
3: parser the expr_string and evaluate it every time call it
4: when
DefaultIsExpris true, we should ignore the default cache in insert cases and evaluate the value every time be called.Check List
Tests
Release note