[CALCITE-7546] NullPointerException in SqlToRelConverter for UNNEST(array) AS alias under conformance with allowAliasUnnestItems=true#4962
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…rray) AS alias under conformance with allowAliasUnnestItems=true Under a SqlConformance where allowAliasUnnestItems() is true (SqlConformanceEnum.PRESTO and user conformances overriding the flag), the AS branch in convertFrom passes fieldNames=null to convertUnnest when the AS clause omits a column list. The PRESTO-only branch then called requireNonNull(fieldNames, "fieldNames") and threw NPE. Fall back to default item aliases derived from SqlUtil#deriveAliasFromOrdinal, matching the names that SqlUnnestOperator#inferReturnType uses during validation. This keeps the relational row type aligned with the validator's underlying namespace so both struct and scalar element types resolve correctly.
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mihaibudiu
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May 24, 2026
mihaibudiu
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| * NullPointerException in SqlToRelConverter for UNNEST(array) AS alias under | ||
| * conformance with allowAliasUnnestItems=true</a>. | ||
| */ | ||
| @Test void testAliasUnnestArrayPlanWithoutColumnList() { |
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Neither of the test cases here matches the one in the issue, but they look close enough.
I hope that you have validated that the test in the issue passes as well.
… reproduction
Add testAliasUnnestArrayLiteralPlanWithoutColumnList using the exact SQL
from the issue ("SELECT t FROM UNNEST(ARRAY[1, 2, 3]) AS t"), which
exercises the same convertUnnest fallback as the column-reference cases
but through a standalone (non-correlated) Uncollect tree. Verified that
the new test reproduces "NullPointerException: fieldNames" against the
pre-fix code and passes with the fix.
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Summary
SqlToRelConverterthrowsNullPointerException: fieldNamesforUNNEST(<array>) AS <alias>(no column list) under a conformance whoseallowAliasUnnestItems()returns true (SqlConformanceEnum.PRESTO, plus user conformances overriding the flag).convertFrom'sASbranch passesfieldNames=nulltoconvertUnnestwhen the AS clause omits a column list. The PRESTO-only branch then calledrequireNonNull(fieldNames, "fieldNames")and threw NPE.SqlUtil#deriveAliasFromOrdinal, matching the names thatSqlUnnestOperator#inferReturnTypeuses during validation. This keeps the relational row type aligned with the validator's underlying namespace, so both struct (e.g.UNNEST(d.employees) AS e→e.empno) and scalar element types (e.g.UNNEST(d.admins) AS a→a) resolve correctly.Test plan
testAliasUnnestArrayPlanWithoutColumnList(struct array, PRESTO) — reproduces the NPE onmain, passes after the fix.testAliasUnnestScalarArrayPlanWithoutColumnList(scalar varchar array, PRESTO).testAliasUnnestArrayPlanWithSingleColumn,testAliasUnnestArrayPlanWithDoubleColumn,testUnnestArrayPlan,testUnnestArrayPlanAs.SqlToRelConverterTest(663) andRelToSqlConverterTest(579) suites pass.