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evalengine: Implement SUBSTRING #14899

Merged
merged 2 commits into from
Jan 9, 2024
Merged

evalengine: Implement SUBSTRING #14899

merged 2 commits into from
Jan 9, 2024

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dbussink
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@dbussink dbussink commented Jan 7, 2024

This implements SUBSTRING (and the SUBSTR alias) in the evalengine.

Also fixes some unsupported calls to be more explicit with a separate error type for regexp. Those don't end up really unsupported, but we then compile a slow path. Also implement some cases that are trivial to do.

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Part of #9647

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vitess-bot bot commented Jan 7, 2024

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@vitess-bot vitess-bot bot added NeedsBackportReason If backport labels have been applied to a PR, a justification is required NeedsDescriptionUpdate The description is not clear or comprehensive enough, and needs work NeedsIssue A linked issue is missing for this Pull Request NeedsWebsiteDocsUpdate What it says labels Jan 7, 2024
@github-actions github-actions bot added this to the v19.0.0 milestone Jan 7, 2024
dbussink
dbussink commented Jan 7, 2024
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go/vt/vtgate/evalengine/expr_compare.go
@@ -568,7 +568,7 @@ func (expr *InExpr) compile(c *compiler) (ctype, error) {

return ctype{Type: sqltypes.Int64, Col: collationNumeric, Flag: flagIsBoolean | (nullableFlags(lhs.Flag) | (rt.Flag & flagNullable))}, nil
case *BindVariable:
return ctype{}, c.unsupported(expr)
return ctype{}, vterrors.Errorf(vtrpcpb.Code_INTERNAL, "rhs of an In operation should be a tuple")
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This matches the error from the evaluator in the compiler here.

go/vt/vtgate/evalengine/expr_convert.go
@@ -205,7 +205,7 @@ func (conv *ConvertExpr) compile(c *compiler) (ctype, error) {
convt = c.compileToFloat(arg, 1)

case "FLOAT":
return ctype{}, c.unsupported(conv)
return ctype{}, conv.returnUnsupportedError()
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Same to match the evaluation path.

go/vt/vtgate/evalengine/fn_compare.go
@@ -354,7 +354,7 @@ func (call *builtinMultiComparison) compile(c *compiler) (ctype, error) {
case sqltypes.Null:
nullable = true
default:
return ctype{}, c.unsupported(call)
panic("unexpected argument type")
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Here as well, we panic in the evaluator too.

go/vt/vtgate/evalengine/fn_string.go
@@ -817,7 +822,7 @@ func (expr *builtinStrcmp) compile(c *compiler) (ctype, error) {
return ctype{Type: sqltypes.Int64, Col: collationNumeric, Flag: nullableFlags(lt.Flag | rt.Flag)}, nil
}

func (call builtinTrim) eval(env *ExpressionEnv) (eval, error) {
func (call *builtinTrim) eval(env *ExpressionEnv) (eval, error) {
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Incorrectly was not using pointer receivers, so fixing this up.

@dbussink dbussink added Type: Enhancement Logical improvement (somewhere between a bug and feature) Component: Evalengine changes to the evaluation engine and removed NeedsDescriptionUpdate The description is not clear or comprehensive enough, and needs work NeedsWebsiteDocsUpdate What it says NeedsIssue A linked issue is missing for this Pull Request NeedsBackportReason If backport labels have been applied to a PR, a justification is required labels Jan 7, 2024
@dbussink dbussink force-pushed the evalengine-substring branch from 8cab716 to c002cfa Compare January 7, 2024 15:13
mdlayher
mdlayher reviewed Jan 8, 2024
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I don't have a ton of context here, just offering some suggestions.

go/vt/vtgate/evalengine/fn_string.go
@@ -932,6 +937,105 @@ func (call builtinTrim) compile(c *compiler) (ctype, error) {
return ctype{Type: sqltypes.VarChar, Flag: flagNullable, Col: col}, nil
}

func (call *builtinSubstring) eval(env *ExpressionEnv) (eval, error) {
str, err := call.Arguments[0].eval(env)
if err != nil || str == nil {
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Note that line 943 could return nil, nil if str is also nil, is that acceptable?

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Not sure what you mean here? We can't lose the error here?

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Hypothetically a return from eval of (nil, nil) would mean that a nil eval and nil error get returned from the function. Is that okay?

I just mention it because I notice all calls to eval have to check both values, which means that it may be possible to simplify a bit by only having the result be valid when err != nil. That would be a larger refactor.

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@mdlayher Yep, nil, nil is ok. A SQL NULL inside the evalengine is represented as the Go nil. So it's a perfectly possible and valid value here.

go/vt/vtgate/evalengine/fn_string.go Show resolved Hide resolved
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@dbussink
evalengine: Implement SUBSTRING
f9ce09c 
This implements `SUBSTRING` (and the `SUBSTR` alias) in the
`evalengine`.

Also fixes some unsupported calls to be more explicit with a separate
error type for regexp. Those don't end up really unsupported, but we
then compile a slow path. Also implement some cases that are trivial to
do.

Signed-off-by: Dirkjan Bussink <d.bussink@gmail.com>
@dbussink dbussink force-pushed the evalengine-substring branch from c002cfa to f9ce09c Compare January 8, 2024 13:13
GuptaManan100
GuptaManan100 approved these changes Jan 9, 2024
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Just a couple of nits, rest looks good to me!

go/vt/vtgate/evalengine/compiler_asm.go Outdated Show resolved Hide resolved
go/vt/vtgate/evalengine/compiler_asm.go Outdated Show resolved Hide resolved
@dbussink
Reduce duplication
6c64022 
Signed-off-by: Dirkjan Bussink <d.bussink@gmail.com>
@dbussink dbussink merged commit fab65bf into vitessio:main Jan 9, 2024
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@dbussink dbussink deleted the evalengine-substring branch January 9, 2024 12:59
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@mdlayher mdlayher mdlayher left review comments

@GuptaManan100 GuptaManan100 GuptaManan100 approved these changes

@systay systay systay approved these changes

@harshit-gangal harshit-gangal Awaiting requested review from harshit-gangal harshit-gangal is a code owner

@frouioui frouioui Awaiting requested review from frouioui frouioui is a code owner

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Component: Evalengine changes to the evaluation engine Type: Enhancement Logical improvement (somewhere between a bug and feature)
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@dbussink @systay @mdlayher @GuptaManan100