Improved Compatibility Around LAST_INSERT_ID - evalengine

[systay]

Description

This PR improves LAST_INSERT_ID(x) behavior to align more closely with MySQL in various scenarios.

• EvalEngine Enhancement: We now handle LAST_INSERT_ID(x) queries directly in vtgate, allowing “dual-only” queries without sending them downstream to MySQL.

select last_insert_id(123);

• VTGate-Calculated Values: Queries like:

SELECT last_insert_id(count(*)) FROM user WHERE foo = 'bar';

can be processed at vtgate level (aggregation across shards), rather than relying on MySQL for the final result.

Limitation

• MySQL sets the session’s LAST_INSERT_ID value to the last row returned in ordered queries such as:

SELECT last_insert_id(col) FROM table ORDER BY foo;

In Vitess, we do not guarantee that the last row dictates the session value. The session’s LAST_INSERT_ID might be derived from a different row.

---

This PR contains commits from #17408

When merging this, please also merge the docs PR: vitessio/website#1913

Related Issue(s)

Checklist

• "Backport to:" labels have been added if this change should be back-ported to release branches
• If this change is to be back-ported to previous releases, a justification is included in the PR description
• Tests were added or are not required
• Did the new or modified tests pass consistently locally and on CI?
• Documentation was added or is not required

[vitess-bot]

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[harshit-gangal]

This PR should handle all the insert cases for last_insert_id

[harshit-gangal]

this should not be skipped

[systay]

it needs to be skipped. we keep getting primary key violations if we don't skip it

[harshit-gangal]

looks good overall,
Let's update website doc for compatibility and mention the limitations and new support added.

[systay]

Added docs vitessio/website#1913