[lqiu96]

Summary

Avoids per-cell String.toLowerCase() allocations when reading rows by column name (FieldValueList.get(String) -> FieldList.getIndex(String)).

Every row in a result set shares the same FieldList schema, so getIndex(name) runs once per cell lookup. Previously, FieldList used a CaseInsensitiveMap that called key.toString().toLowerCase() on every get(name) call:

• For any column name containing uppercase letters (for example, "UserName"), .toLowerCase() allocated a new String on every cell read across every row.
• Even for lowercase column names, .toLowerCase() scanned every character of the name on every lookup.

Changes

• FieldList:
  • Pre-size a HashMap with Maps.newHashMapWithExpectedSize(size * 2) and populate both name.toLowerCase(Locale.ROOT) and exact-case name (when different) once when building the schema.
  • Preserve last-writer-wins behavior if two fields differ only by case (for example, "FOO" at index 0 followed by "foo" at index 1).
  • In getIndex(String), probe nameIndex.get(name) first so exact schema names and all-lowercase names hit with zero allocations, falling back to name.toLowerCase(Locale.ROOT) only on a miss.
• FieldListTest:
  • Added testGetIndexExactLowerAndMixedCase and testGetIndexCaseCollisionPreservesLastWriterWins.

Verification

• mvn test -pl java-bigquery/google-cloud-bigquery -Dtest=FieldListTest (6 passed)
• mvn test -pl java-bigquery/google-cloud-bigquery -Dtest=SchemaTest (3 passed)
• mvn test -pl java-bigquery/google-cloud-bigquery -Dtest=FieldValueListTest (5 passed)
• mvn test -pl java-bigquery/google-cloud-bigquery -Dtest=FieldTest (12 passed)

[gemini-code-assist]

Code Review

This pull request optimizes field index lookups in FieldList by pre-storing both exact-case and lowercase field names in a single map, avoiding string allocation and lowercasing on every lookup when exact or lowercase matches are found. It also ensures that the existing last-writer-wins behavior is preserved in case of case collisions. Unit tests have been added to verify these changes. I have no feedback to provide.