[lqiu96]

Summary & Bottleneck

When decoding BigQuery table rows and query results, every boolean cell ("true" or "false") previously allocated a new 24-byte FieldValue wrapper in FieldValue.fromPb / FieldValue.of ($O(\text{rows} \times \text{boolean_cols})$ allocations), even though FieldValue is deeply immutable and stores the canonical "true" or "false" string value.

• In addition, FieldValue.getBooleanValue() executed stringValue.equalsIgnoreCase("true") twice on every true cell (once in checkState and a second time inside Boolean.parseBoolean(stringValue)).

Changes

• In java-bigquery/google-cloud-bigquery/src/main/java/com/google/cloud/bigquery/FieldValue.java:
  • Add reusable immutable flyweight singletons for primitive "true" and "false" cells (TRUE_PRIMITIVE, FALSE_PRIMITIVE, TRUE_PRIMITIVE_INT64_TIMESTAMPS, and FALSE_PRIMITIVE_INT64_TIMESTAMPS).
  • Return the flyweight singletons in FieldValue.of(Attribute, Object, Boolean) (invoked by FieldValue.fromPb) and in readResolve() when attribute == Attribute.PRIMITIVE, useInt64Timestamps != null, and value is "true" or "false".
  • Simplify getBooleanValue() to check "true".equalsIgnoreCase(stringValue) and "false".equalsIgnoreCase(stringValue) once before throwing IllegalStateException.
• In java-bigquery/google-cloud-bigquery/src/test/java/com/google/cloud/bigquery/FieldValueTest.java:
  • Add unit test testBooleanFlyweightsAndGetBooleanValue verifying singleton reuse across FieldValue.of and FieldValue.fromPb as well as case-insensitive and invalid boolean parsing.

Expected Impact

• Eliminates 100% of FieldValue wrapper allocations on boolean columns across query results and table data reads.
• Eliminates redundant case-insensitive string comparisons in FieldValue.getBooleanValue().

Verification

• Ran unit tests in FieldValueTest and FieldValueListTest:
  mvn test -pl java-bigquery/google-cloud-bigquery -Dtest=FieldValueTest,FieldValueListTest