fix(unparser): make BigQueryDialect more robust#21296
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alamb merged 3 commits intoApr 19, 2026
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Thanks @sgrebnov, I doubled checked with sqlglot and LGTM.
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## Which issue does this PR close? PR improves `BigQueryDialect` dialect to make generated SQL `BigQuery`-compatible (fix execution errors). ## What changes are included in this PR? Eight `Dialect` trait overrides added to `BigQueryDialect`: https://docs.cloud.google.com/bigquery/docs/reference/standard-sql/data-types 1. `date_field_extract_style` → `Extract` + `scalar_function_to_sql_overrides` BigQuery does not support `date_part()`. TPC-H Q7, Q8, Q9 fail with `Function not found: date_part`. | Before (error) | After | |---|---| | `date_part('YEAR', l_shipdate)` | `EXTRACT(YEAR FROM l_shipdate)` | 2. `interval_style` → `SQLStandard` BigQuery does not support PostgreSQL-style interval abbreviations. TPC-H Q4, Q20 fail with `Syntax error: Unexpected ")"`. | Before (error) | After | |---|---| | `INTERVAL '3 MONS'` | `INTERVAL '3' MONTH` | 3. `float64_ast_dtype` → `Float64` BigQuery does not support `DOUBLE`. Fails with `Type not found: DOUBLE`. | Before (error) | After | |---|---| | `CAST(a AS DOUBLE)` | `CAST(a AS FLOAT64)` | 4. `supports_column_alias_in_table_alias` → `false` BigQuery does not support column aliases in table alias definitions. Fails with `Expected ")" but got "("`. | Before (error) | After | |---|---| | `SELECT c.key FROM (...) AS c(key)` | `SELECT c.key FROM (SELECT o_orderkey AS key FROM orders) AS c` | 5. `utf8_cast_dtype` + `large_utf8_cast_dtype` → `String` BigQuery does not support `VARCHAR`/`TEXT`. Fails with `Type not found: VARCHAR`, `Type not found: Text`. | Before (error) | After | |---|---| | `CAST(a AS VARCHAR)` | `CAST(a AS STRING)` | | `CAST(a AS TEXT)` | `CAST(a AS STRING)` | 6. ~`int64_cast_dtype` → `Int64`~ 7. `timestamp_cast_dtype` → `Timestamp` (no timezone qualifier) https://docs.cloud.google.com/bigquery/docs/reference/standard-sql/data-types#timestamp_type BigQuery does not support `TIMESTAMP WITH TIME ZONE`. Fails with `Syntax error: Expected ')' or keyword FORMAT but got keyword WITH`. `TIMESTAMP` should be used (preserves time zone information)/ | Before (error) | After | |---|---| | `CAST(a AS TIMESTAMP WITH TIME ZONE)` | `CAST(a AS TIMESTAMP)` | ## Are these changes tested? Yes. Added `test_bigquery_dialect_overrides` unit test covering all eight overrides, verified against BigQuery before and after. ## Are there any user-facing changes? No API changes. `BigQueryDialect` now generates valid BigQuery SQL for the affected expressions.
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Which issue does this PR close?
PR improves
BigQueryDialectdialect to make generated SQLBigQuery-compatible (fix execution errors).What changes are included in this PR?
Eight
Dialecttrait overrides added toBigQueryDialect:https://docs.cloud.google.com/bigquery/docs/reference/standard-sql/data-types
date_field_extract_style→Extract+scalar_function_to_sql_overridesBigQuery does not support
date_part(). TPC-H Q7, Q8, Q9 fail withFunction not found: date_part.date_part('YEAR', l_shipdate)EXTRACT(YEAR FROM l_shipdate)interval_style→SQLStandardBigQuery does not support PostgreSQL-style interval abbreviations. TPC-H Q4, Q20 fail with
Syntax error: Unexpected ")".INTERVAL '3 MONS'INTERVAL '3' MONTHfloat64_ast_dtype→Float64BigQuery does not support
DOUBLE. Fails withType not found: DOUBLE.CAST(a AS DOUBLE)CAST(a AS FLOAT64)supports_column_alias_in_table_alias→falseBigQuery does not support column aliases in table alias definitions. Fails with
Expected ")" but got "(".SELECT c.key FROM (...) AS c(key)SELECT c.key FROM (SELECT o_orderkey AS key FROM orders) AS cutf8_cast_dtype+large_utf8_cast_dtype→StringBigQuery does not support
VARCHAR/TEXT. Fails withType not found: VARCHAR,Type not found: Text.CAST(a AS VARCHAR)CAST(a AS STRING)CAST(a AS TEXT)CAST(a AS STRING)int64_cast_dtype→Int64timestamp_cast_dtype→Timestamp(no timezone qualifier)https://docs.cloud.google.com/bigquery/docs/reference/standard-sql/data-types#timestamp_type
BigQuery does not support
TIMESTAMP WITH TIME ZONE. Fails withSyntax error: Expected ')' or keyword FORMAT but got keyword WITH.TIMESTAMPshould be used (preserves time zone information)/CAST(a AS TIMESTAMP WITH TIME ZONE)CAST(a AS TIMESTAMP)Are these changes tested?
Yes. Added
test_bigquery_dialect_overridesunit test covering all eight overrides, verified against BigQuery before and after.Are there any user-facing changes?
No API changes.
BigQueryDialectnow generates valid BigQuery SQL for the affected expressions.