vitessdriver: send string for binary result values

[derekperkins]

Description

Apologies, my prior PR in #19527 did the string conversion the wrong direction, coming out of Vitess vs going into Vitess. This reverts that change and does a similar conversion before building the bind variable.

Related Issue(s)

• fixes v23 regression: inserting JSON values throws an error #19181
• reverts vitessdriver: return string for binary result values #19527

Checklist

• "Backport to:" labels have been added if this change should be back-ported to release branches
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• Tests were added or are not required
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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.26%. Comparing base (70c7a72) to head (594b11c).
⚠️ Report is 168 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main   #19542       +/-   ##
===========================================
+ Coverage   69.67%   78.26%    +8.58%     
===========================================
  Files        1614        5     -1609     
  Lines      216793      483   -216310     
===========================================
- Hits       151044      378   -150666     
+ Misses      65749      105    -65644     

Flag	Coverage Δ
partial	78.26% <100.00%> (?)

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[promptless]

📝 Documentation updates detected!

Updated existing suggestion: Remove changelog entry for vitessdriver binary-to-string change (reverted)

---

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[arthurschreiber]

Can you add a test case for this? Maybe a unit test and an integration level test would be good.

[dbussink]

You'll also will need to fix the DCO here.

[derekperkins]

I wasn't quite sure what the right behavior here was. There are three outcomes:

• NullBindVariable: what is happening here, which is an untyped null
• Typed NULL as VARBINARY: this is the only one I'm fairly confident that we don't want, as it is likely to trigger a similar error for json values
• Typed NULL as VARCHAR: this maintains the spirit of the string conversion here, but may be unnecessary

Is there any reason to choose a typed null over what is currently happening? This has to happen before the string conversion because string isn't nullable natively

[derekperkins]

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[mattlord]

Nit, but we should use require in new tests.

[derekperkins]

changed and I added a commit migrating the rest of the vitessdriver tests to require

[Copilot]

Pull request overview

Updates vitessdriver parameter binding to avoid sending []byte inputs as VARBINARY (which can trigger MySQL JSON charset errors), while reverting the earlier behavior change that affected how binary-typed result values are returned to Go callers.

Changes:

• Revert ToNative behavior so binary result values remain []byte (undoing the prior “return string for binary results” approach).
• Update BuildBindVariable to convert []byte inputs into VARCHAR bind variables (and nil []byte into NULL) before sending to Vitess.
• Refactor several vitessdriver tests to use testify/require assertions and add targeted tests for BuildBindVariable.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
go/vt/vitessdriver/convert.go	Moves the “bytes->string” conversion to bind-var construction (inputs), and removes the binary special-case from result conversion (outputs).
go/vt/vitessdriver/convert_test.go	Updates ToNative expectations for binary types and adds new coverage for BuildBindVariable.
go/vt/vitessdriver/driver_test.go	Converts many assertions to require and improves subtest isolation with t.Run.
go/vt/vitessdriver/rows_test.go	Converts comparisons to require and removes now-unneeded mismatch logging helper.
go/vt/vitessdriver/streaming_rows_test.go	Converts comparisons/error checks to require and removes unused imports.