[sjvanrossum]

Fixes four correctness bugs across Row, RowWithGetters, RowUtils, and SchemaCoderHelpers.LogicalTypeCoder.

Row.Equals.deepHashCode previously passed the logical input value directly when recursing on fieldType.getLogicalType().getBaseType() without converting to the logical type's base value via SchemaUtils.toLogicalBaseType(logicalType, a). When the base type was BYTES (or a collection/map) and the input type was not byte[] (e.g. ByteBuffer), deepHashCode threw a ClassCastException even though Row.Equals.deepEquals converted to the base type first. RowWithGetters.equals only returned true when comparing two RowWithGetters instances if Objects.equals(getterTarget, other.getterTarget) held, failing when the backing POJO/Bean did not override Object.equals, and RowWithGetters.hashCode hashed (getSchema(), getterTarget) instead of the row's field values, violating the Object.hashCode contract whenever a RowWithGetters was compared against an equivalent RowWithStorage.

RowUtils.FieldValueBuilder.processRow previously returned an existing Row value without checking whether its schema matched the expected field schema, allowing Rows with mismatched nested schemas (both in ROW fields and inside collections/maps of ROW) to be constructed when field verification was bypassed or used via FieldValueBuilder.

RowUtils previously called ((ByteBuffer) value).array() directly when converting ByteBuffer values for BYTES fields. This threw UnsupportedOperationException on read-only or direct ByteBuffers and silently ignored position(), limit(), and arrayOffset() on sliced/wrapped buffers, returning the entire backing array instead of the buffer's active slice.

LogicalTypeCoder.encode converted ReadableInstant base values to org.joda.time.Instant (as required by InstantCoder), but structuralValue, isRegisterByteSizeObserverCheap, and registerByteSizeObserver called logicalType.toBaseType(value) directly without converting ReadableInstant to Instant (and without guarding against null), causing a ClassCastException in InstantCoder.

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📋 Review Summary

This PR fixes four distinct correctness issues across Row, RowWithGetters, RowUtils, and SchemaCoderHelpers.LogicalTypeCoder, ensuring proper equality/hashing contracts, nested Row schema validation, ByteBuffer slice/read-only conversion, and DATETIME logical type base conversions.

🔍 General Feedback

• The fixes are clean, minimal, and directly address the root causes of each bug.
• Unit test coverage across RowTest, JavaFieldSchemaTest, and RowCoderTest thoroughly exercises all four fixes.

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