ESQL: Fix INLINE STATS GROUP BY null being incorrectly pruned (#140027)#141095
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elasticsearchmachine merged 1 commit intoelastic:9.3from Jan 22, 2026
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ESQL: Fix INLINE STATS GROUP BY null being incorrectly pruned (#140027)#141095elasticsearchmachine merged 1 commit intoelastic:9.3from
INLINE STATS GROUP BY null being incorrectly pruned (#140027)#141095elasticsearchmachine merged 1 commit intoelastic:9.3from
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…tic#140027) This PR fixes the issue where `INLINE STATS GROUP BY null` was being incorrectly pruned by `PruneLeftJoinOnNullMatchingField`. Fixes elastic#139887 ## Problem For query: ``` FROM employees | INLINE STATS c = COUNT(*) BY n = null | KEEP c, n | LIMIT 3 ``` During `LogicalPlanOptimizer`: ``` Limit[3[INTEGER],false,false] \_EsqlProject[[c{r}elastic#2, n{r}elastic#4]] \_InlineJoin[LEFT,[n{r}elastic#4],[n{r}elastic#4]] |_Eval[[null[NULL] AS n#4]] | \_EsRelation[employees][<no-fields>{r$}elastic#7] \_Aggregate[[n{r}elastic#4],[COUNT(*[KEYWORD],true[BOOLEAN],PT0S[TIME_DURATION]) AS c#2, n{r}elastic#4]] \_StubRelation[[<no-fields>{r$}elastic#7, n{r}elastic#4]] ``` The following join node: ``` InlineJoin[LEFT,[n{r}elastic#4],[n{r}elastic#4]] |_Eval[[null[NULL] AS n#4]] | \_EsRelation[employees][<no-fields>{r$}elastic#7] \_Aggregate[[n{r}elastic#4],[COUNT(*[KEYWORD],true[BOOLEAN],PT0S[TIME_DURATION]) AS c#2, n{r}elastic#4]] \_StubRelation[[<no-fields>{r$}elastic#7, n{r}elastic#4]] ``` should NOT have `PruneLeftJoinOnNullMatchingField` applied, because the right side is an `Aggregate` (originating from `INLINE STATS`). Since `STATS` supports `GROUP BY null`, the join key being null is a valid use case. Pruning this join would incorrectly eliminate the aggregation results, changing the query semantics. During `LocalLogicalPlanOptimizer`: ``` ProjectExec[[c{r}elastic#2, n{r}elastic#4]] \_LimitExec[3[INTEGER],null] \_ExchangeExec[[c{r}elastic#2, n{r}elastic#4],false] \_FragmentExec[filter=null, estimatedRowSize=0, reducer=[], fragment=[<> Project[[c{r}elastic#2, n{r}elastic#4]] \_Limit[3[INTEGER],false,false] \_InlineJoin[LEFT,[n{r}elastic#4],[n{r}elastic#4]] |_Eval[[null[NULL] AS n#4]] | \_EsRelation[employees][<no-fields>{r$}elastic#7] \_LocalRelation[[c{r}elastic#2, n{r}elastic#4],Page{blocks=[LongVectorBlock[vector=ConstantLongVector[positions=1, value=100]], ConstantNullBlock[positions=1]]}]<>]] ``` The following join node: ``` InlineJoin[LEFT,[n{r}elastic#4],[n{r}elastic#4]] |_Eval[[null[NULL] AS n#4]] | \_EsRelation[employees][<no-fields>{r$}elastic#7] \_LocalRelation[[c{r}elastic#2, n{r}elastic#4],Page{blocks=[LongVectorBlock[vector=ConstantLongVector[positions=1, value=100]], ConstantNullBlock[positions=1]]}] ``` should NOT have `PruneLeftJoinOnNullMatchingField` applied, because the right side is a `LocalRelation` (the `Aggregate` was optimized into a `LocalRelation` containing the pre-computed aggregation results). Pruning this join when the join key is null would discard the valid aggregation results stored in the `LocalRelation`, incorrectly producing null values instead of the expected count. ## Solution The fix ensures that `PruneLeftJoinOnNullMatchingField` only applies to `LOOKUP JOIN` nodes, where `join.right()` is an `EsRelation`. For `INLINE STATS` joins, the right side can be: - `Aggregate` (before optimization), or - `LocalRelation` (after the aggregate is optimized) By checking `join.right() instanceof EsRelation`, we correctly skip the pruning optimization for `INLINE STATS` joins, preserving the expected query results when grouping by null. (cherry picked from commit f3ccb70)
astefan
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Backports #140027