feat(duckdb): convert ARRAY_AGG IGNORE NULLS to FILTER clause#7893
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BigQuery's `ARRAY_AGG(x IGNORE NULLS ...)` silently drops NULLs from the aggregation. DuckDB does not support `IGNORE NULLS` on aggregate functions, but the same semantics can be expressed with a `FILTER` clause: `ARRAY_AGG(x ...) FILTER(WHERE x IS NOT NULL)`. Previously, the DuckDB generator silently dropped the `IGNORE NULLS` modifier on `ARRAY_AGG`, producing incorrect results when the input contained NULL values. Adds: - `ArrayAgg`-specific handling in `ignorenulls_sql` that sets a `nulls_excluded` flag, which the existing `_add_arrayagg_null_filter` infrastructure converts to a `FILTER(WHERE col IS NOT NULL)` clause - `arrayagg_sql` override to unwrap `Order`/`Limit` nodes so the FILTER clause references the correct column expression - Updated test expectations for ARRAY_AGG DISTINCT IGNORE NULLS
geooo109
reviewed
Jul 17, 2026
geooo109
reviewed
Jul 17, 2026
geooo109
reviewed
Jul 19, 2026
- Move Order/Limit unwrapping from DuckDB override to base generator's arrayagg_sql so all dialects benefit - Emit unsupported warning for LIMIT inside ARRAY_AGG in DuckDB - Remove invalid LIMIT 1, 10 test (unsupported BigQuery syntax) - Simplify DuckDB arrayagg_sql to delegate to super() Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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@sirockin is this still a draft? What's pending? |
geooo109
marked this pull request as ready for review
July 21, 2026 11:17
geooo109
approved these changes
Jul 21, 2026
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Summary
BigQuery's
ARRAY_AGG(x IGNORE NULLS ...)silently drops NULLs from the aggregation. DuckDB does not supportIGNORE NULLSon aggregate functions, but the same semantics can be expressed with aFILTERclause:ARRAY_AGG(x ...) FILTER(WHERE x IS NOT NULL).Problem
Previously, the DuckDB generator silently dropped the
IGNORE NULLSmodifier onARRAY_AGG, producing incorrect results when the input contained NULL values. Theignorenulls_sqlmethod handled window functions (viaIGNORE_RESPECT_NULLS_WINDOW_FUNCTIONS) and convertedFirsttoAnyValue, butArrayAggwas not handled — theIGNORE NULLSwas silently lost.Changes
ArrayAgg-specific handling inignorenulls_sqlthat sets anulls_excludedflag, which the existing_add_arrayagg_null_filterinfrastructure converts to aFILTER(WHERE col IS NOT NULL)clausearrayagg_sqloverride to unwrapOrder/Limitnodes so the FILTER clause references the correct column expression (not the ordering wrapper)ARRAY_AGG DISTINCT IGNORE NULLSto include theFILTERclauseMotivation
We use sqlglot to transpile BigQuery SQL models to DuckDB for local testing via sqlmesh. Our production models use
ARRAY_AGG(... IGNORE NULLS ORDER BY ...)extensively, and the silent loss ofIGNORE NULLScaused incorrect test results.