expression: add simple expression semantic equal check logic #43558
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Signed-off-by: AilinKid <314806019@qq.com>
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Signed-off-by: AilinKid <314806019@qq.com>
| sc := ctx.GetSessionVars().StmtCtx | ||
| sc.CanonicalHashCode.Store(true) | ||
| defer sc.CanonicalHashCode.Store(false) | ||
| return bytes.Equal(expr1.HashCode(sc), expr2.HashCode(sc)) |
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(*ScalarFunction).HashCode is not a pure function and has the side effect(i.e., if len(sf.hashcode) > 0, then we don't need to recalculate it). Is it ok to expose the hash code calculated under CanonicalHashCode mode to outside?
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Nice catch!
Addressed.
expression/scalar_function.go
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| if !ok { | ||
| // use the origin arg hash code. | ||
| for _, argCode := range argsHashCode { | ||
| sf.hashcode = append(sf.hashcode, argCode...) |
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Do we need to encode the not op?
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Nope：
Expression1: not(a<b)
Expression2: a>=b
Expression1 and Expression2 should have the same hashcode, we try to disintegrate the NOT into a mathematical operation convertion.
Signed-off-by: AilinKid <314806019@qq.com>
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/merge |
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This pull request has been accepted and is ready to merge. Commit hash: ecae432
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What problem does this PR solve?
Issue Number: close #43572
Problem Summary:
What is changed and how it works?
In TiDB Expression tree, sometimes we may need judge whether two expression tree are semantic equal,
this PR adds the simple check logic ported from SparkSQL.
Check List
Tests
Side effects
Documentation
Release note
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