Deep copy BytesRef when creating a constant vector block

[dnhatn]

Currently, when creating a constant BytesRef block or vector from a constant input, we do not deep copy the BytesRef in the evaluator. As a result, if the evaluator generates additional blocks afterwards, these blocks may share the underlying bytes with the constant block, leading to incorrect data. This issue was seen in tests where two rows had the same data when they should not.

For example:

elasticsearch/x-pack/plugin/esql/src/main/generated/org/elasticsearch/xpack/esql/expression/function/scalar/convert/ParseIpLeadingZerosAreDecimalEvaluator.java

Line 54 in f32c348

return driverContext.blockFactory().newConstantBytesRefBlockWith(evalValue(vector, 0, scratchPad), positionCount);

and

elasticsearch/x-pack/plugin/esql/src/main/generated/org/elasticsearch/xpack/esql/expression/function/scalar/convert/UrlDecodeEvaluator.java

Line 48 in 1af8b3e

return driverContext.blockFactory().newConstantBytesRefBlockWith(evalValue(vector, 0, scratchPad), positionCount);

In these cases, a constant BytesRef is created from the same bytesView of BreakingBytesRefBuilder.

For other vector/block types, we already copy the BytesRef to a new buffer, but this is not done for constant blocks. This change ensures that we always deep copy the input BytesRef when creating a constant vector or block. While in some cases the copy may not be necessary, the overhead is minimal and this approach is safer than requiring callers to handle the copy selectively.

Closes #140809
Closes #140621
Closes #140615

[elasticsearchmachine]

Hi @dnhatn, I've created a changelog YAML for you.

[elasticsearchmachine]

Hi @dnhatn, I've updated the changelog YAML for you.

[elasticsearchmachine]

Pinging @elastic/es-analytical-engine (Team:Analytics)

[dnhatn]

Thanks Nik!

[elasticsearchmachine]

💔 Backport failed

Status	Branch	Result
✅	9.3
❌	8.19	Commit could not be cherrypicked due to conflicts
✅	9.2

You can use sqren/backport to manually backport by running backport --upstream elastic/elasticsearch --pr 141242