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…r_iceberg enable prewhere for iceberg
…ere-external-columns Fix exception in Parquet PREWHERE when column is not in file
…o-assertion Fix exception in `updateFormatPrewhereInfo` when only row-level filter is set
…bled The Iceberg read optimization (`allow_experimental_iceberg_read_optimization`) identifies constant columns from Iceberg metadata and removes them from the read request. When all requested columns become constant, it sets `need_only_count = true`, which tells the Parquet reader to skip all initialization — including `preparePrewhere` — and just return the raw row count from file metadata. This completely bypasses `row_level_filter` (row policies) and `prewhere_info`, returning unfiltered row counts. The InterpreterSelectQuery relies on the storage to apply these filters when `supportsPrewhere` is true and does not add a fallback FilterStep to the query plan, so the filter is silently lost. The fix prevents `need_only_count` from being set when an active `row_level_filter` or `prewhere_info` exists in the format filter info. Fixes #1595
…ss instead of rows_total
…t NULLs The Altinity-specific constant column optimization (`allow_experimental_iceberg_read_optimization`) scans `requested_columns` for nullable columns absent from the Iceberg file metadata and replaces them with constant NULLs. However, `requested_columns` can also contain columns produced by `prewhere_info` or `row_level_filter` expressions (e.g. `equals(boolean_col, false)`). These computed columns are not in the file metadata, and their result type is often `Nullable(UInt8)`, so the optimization incorrectly treats them as missing file columns and replaces them with NULLs. This corrupts the prewhere pipeline: the Parquet reader evaluates the filter expression correctly, but the constant column optimization then overwrites the result with NULLs. With `need_filter = false` (old planner, PREWHERE + WHERE), all rows appear to fail the filter, producing empty output. With `need_filter = true`, the filter column is NULL so all rows are filtered out. The fix skips columns that match the `prewhere_info` or `row_level_filter` column names, since these are computed at read time and never stored in the file.
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