iceberg: add configurable Parquet string encoding for Redshift Spectrum compatibility

[josephwoodward]

[claude]

Commits
LGTM

Review
Small, focused change adding a parquet.string_encoding config field on the Iceberg output to opt into plain encoding for Redshift Spectrum compatibility. Threads []parquet.WriterOption through NewRouter → NewWriter → newParquetSink, and the inline config parsing mirrors the existing parseCommitConfig pattern in the same file. The default (delta_length_byte_array) preserves prior behavior.

LGTM

[claude]

Commits
LGTM

Review
PR adds an optional parquet.string_encoding config field to the iceberg output to allow choosing plain over delta_length_byte_array for Redshift Spectrum compatibility. Field constants follow the existing io prefix convention, the optional parquet block is correctly gated via conf.Contains(), the default matches parquet-go's library default (so no option is added unless plain is selected), and pqSchema is placed first in the options slice so user-supplied options can override schema-derived defaults. Test helpers and e2e callers are updated for the new NewRouter/NewWriter parameter.

LGTM

[claude]

Commits
LGTM

Review
Adds an optional parquet.string_encoding field on the iceberg output to switch the Parquet BYTE_ARRAY encoding from delta_length_byte_array to plain for Redshift Spectrum compatibility. The new option is threaded through Router and writer into parquetSink, with the prior behavior preserved by default. Field constants, Optional()/Default() placement, Contains() guard, and error wrapping all follow project patterns.

LGTM

[claude]

This new parquet.string_encoding config field is introduced without any test coverage. Per the project's test patterns, changed code should be accompanied by tests — at minimum a config-parsing/linting test exercising both plain and delta_length_byte_array (and ideally a writer test verifying the option is actually plumbed through to the underlying parquet writer). The existing writer_test.go and router_test.go could be extended for this.

[claude]

Commits

1. Commits iceberg: use switch statement to show options explicitly (77d7709) and iceberg: address linting error (de2b6df) are fixup-style follow-ups to the first commit (bc5417a) that touch the same code paths introduced in that change. They should be squashed into the first commit so the PR lands as a single self-contained logical change, per the granularity rule.

Review

Adds a configurable Parquet string_encoding option (plain or delta_length_byte_array) to the iceberg output to support readers like AWS Redshift Spectrum. The option is plumbed through Router → writer → parquetSink via a []parquet.WriterOption slice. Wiring looks correct.

1. New configuration field is introduced without test coverage — see inline comment on internal/impl/iceberg/output_iceberg.go.