From e88e4c690f29413ce0e8618783f0e33b2e71adcb Mon Sep 17 00:00:00 2001 From: Dimitris Athanasiou Date: Tue, 16 Dec 2025 12:23:26 +0000 Subject: [PATCH 1/2] ES|QL: Fix aggregation on null value This correctly handles aggregations on null values. Aggregations on constants do not work as per https://github.com/elastic/elasticsearch/issues/100634. However, we can do better in terms of handling null. We achieve this by 2 changes: - we do not fold aggregate functions as `AggregateMapper` does not handle `Literal` values. - we reuse the existing `ReplaceStatsFilteredAggWithEval` rule to replace aggs on null with an eval. I have renamed `ReplaceStatsFilteredAggWithEval` to `ReplaceStatsFilteredOrNullAggWithEval` to capture the new scenario where we apply the rule. Closes #137544 --- .../xpack/esql/CsvTestUtils.java | 2 +- .../src/main/resources/stats.csv-spec | 33 ++++++++ .../xpack/esql/action/EsqlCapabilities.java | 11 ++- .../esql/optimizer/LogicalPlanOptimizer.java | 4 +- .../optimizer/rules/logical/FoldNull.java | 3 + ...eplaceStatsFilteredOrNullAggWithEval.java} | 32 +++++-- .../optimizer/LogicalPlanOptimizerTests.java | 3 +- .../rules/logical/FoldNullTests.java | 46 ++++------ ...eStatsFilteredOrNullAggWithEvalTests.java} | 84 ++++++++++++++++++- 9 files changed, 172 insertions(+), 46 deletions(-) rename x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/optimizer/rules/logical/{ReplaceStatsFilteredAggWithEval.java => ReplaceStatsFilteredOrNullAggWithEval.java} (86%) rename x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/optimizer/rules/logical/{ReplaceStatsFilteredAggWithEvalTests.java => ReplaceStatsFilteredOrNullAggWithEvalTests.java} (91%) diff --git a/x-pack/plugin/esql/qa/testFixtures/src/main/java/org/elasticsearch/xpack/esql/CsvTestUtils.java b/x-pack/plugin/esql/qa/testFixtures/src/main/java/org/elasticsearch/xpack/esql/CsvTestUtils.java index a0f3d3e694b96..d09ae7130a041 100644 --- a/x-pack/plugin/esql/qa/testFixtures/src/main/java/org/elasticsearch/xpack/esql/CsvTestUtils.java +++ b/x-pack/plugin/esql/qa/testFixtures/src/main/java/org/elasticsearch/xpack/esql/CsvTestUtils.java @@ -492,7 +492,7 @@ public enum Type { DOUBLE_RANGE(s -> s == null ? null : Arrays.stream(s.split("-")).map(Double::parseDouble).toArray(), double[].class), DATE_RANGE(s -> s == null ? null : Arrays.stream(s.split("-")).map(BytesRef::new).toArray(), BytesRef[].class), VERSION(v -> new org.elasticsearch.xpack.versionfield.Version(v).toBytesRef(), BytesRef.class), - NULL(s -> null, Void.class), + NULL(s -> s, Void.class), DATETIME( x -> x == null ? null : DateFormatters.from(UTC_DATE_TIME_FORMATTER.parse(x)).toInstant().toEpochMilli(), (l, r) -> l instanceof Long maybeIP ? maybeIP.compareTo((Long) r) : l.toString().compareTo(r.toString()), diff --git a/x-pack/plugin/esql/qa/testFixtures/src/main/resources/stats.csv-spec b/x-pack/plugin/esql/qa/testFixtures/src/main/resources/stats.csv-spec index f6adbbfb35faf..abf372dcae296 100644 --- a/x-pack/plugin/esql/qa/testFixtures/src/main/resources/stats.csv-spec +++ b/x-pack/plugin/esql/qa/testFixtures/src/main/resources/stats.csv-spec @@ -3599,3 +3599,36 @@ from airports a:double | b:double | c:long 6.0 | 6.0 | 8 ; + +fixStatsValuesOnReferenceToNullUncasted +required_capability: fix_agg_on_null_by_replacing_with_eval + +ROW x = null +| STATS VALUES(x) +; + +VALUES(x):null +null +; + +fixStatsValuesOnReferenceToNullCasted +required_capability: fix_agg_on_null_by_replacing_with_eval + +ROW x = null::long +| STATS VALUES(x) +; + +VALUES(x):long +null +; + +fixStatsValuesOnLiteralNull +required_capability: fix_agg_on_null_by_replacing_with_eval + +ROW x = 1 +| STATS y = VALUES(null) +; + +y:null +null +; diff --git a/x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/action/EsqlCapabilities.java b/x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/action/EsqlCapabilities.java index 8a27ef9c513ed..394b6a12d68e1 100644 --- a/x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/action/EsqlCapabilities.java +++ b/x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/action/EsqlCapabilities.java @@ -12,6 +12,7 @@ import org.elasticsearch.compute.lucene.read.ValuesSourceReaderOperator; import org.elasticsearch.features.NodeFeature; import org.elasticsearch.rest.action.admin.cluster.RestNodesCapabilitiesAction; +import org.elasticsearch.xpack.esql.optimizer.rules.logical.ReplaceStatsFilteredOrNullAggWithEval; import org.elasticsearch.xpack.esql.plugin.EsqlFeatures; import java.util.ArrayList; @@ -1785,7 +1786,7 @@ public enum Cap { FIX_INLINE_STATS_INCORRECT_PRUNNING(INLINE_STATS.enabled), /** - * {@link org.elasticsearch.xpack.esql.optimizer.rules.logical.ReplaceStatsFilteredAggWithEval} replaced a stats + * {@link ReplaceStatsFilteredOrNullAggWithEval} replaced a stats * with false filter with null with {@link org.elasticsearch.xpack.esql.expression.function.aggregate.Present} or * {@link org.elasticsearch.xpack.esql.expression.function.aggregate.Absent} */ @@ -1801,6 +1802,14 @@ public enum Cap { */ ENABLE_REDUCE_NODE_LATE_MATERIALIZATION(Build.current().isSnapshot()), + /** + * {@link ReplaceStatsFilteredOrNullAggWithEval} now replaces an + * {@link org.elasticsearch.xpack.esql.expression.function.aggregate.AggregateFunction} with null value with an + * {@link org.elasticsearch.xpack.esql.plan.logical.Eval}. + * https://github.com/elastic/elasticsearch/issues/137544 + */ + FIX_AGG_ON_NULL_BY_REPLACING_WITH_EVAL, + // Last capability should still have a comma for fewer merge conflicts when adding new ones :) // This comment prevents the semicolon from being on the previous capability when Spotless formats the file. ; diff --git a/x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/optimizer/LogicalPlanOptimizer.java b/x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/optimizer/LogicalPlanOptimizer.java index 40470f257d4bc..383518407e314 100644 --- a/x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/optimizer/LogicalPlanOptimizer.java +++ b/x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/optimizer/LogicalPlanOptimizer.java @@ -60,7 +60,7 @@ import org.elasticsearch.xpack.esql.optimizer.rules.logical.ReplaceOrderByExpressionWithEval; import org.elasticsearch.xpack.esql.optimizer.rules.logical.ReplaceRegexMatch; import org.elasticsearch.xpack.esql.optimizer.rules.logical.ReplaceRowAsLocalRelation; -import org.elasticsearch.xpack.esql.optimizer.rules.logical.ReplaceStatsFilteredAggWithEval; +import org.elasticsearch.xpack.esql.optimizer.rules.logical.ReplaceStatsFilteredOrNullAggWithEval; import org.elasticsearch.xpack.esql.optimizer.rules.logical.ReplaceStringCasingWithInsensitiveEquals; import org.elasticsearch.xpack.esql.optimizer.rules.logical.ReplaceTrivialTypeConversions; import org.elasticsearch.xpack.esql.optimizer.rules.logical.SetAsOptimized; @@ -206,7 +206,7 @@ protected static Batch operators() { // TODO: bifunction can now (since we now have just one data types set) be pushed into the rule new SimplifyComparisonsArithmetics(DataType::areCompatible), new ReplaceStringCasingWithInsensitiveEquals(), - new ReplaceStatsFilteredAggWithEval(), + new ReplaceStatsFilteredOrNullAggWithEval(), new ExtractAggregateCommonFilter(), // prune/elimination new PruneFilters(), diff --git a/x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/optimizer/rules/logical/FoldNull.java b/x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/optimizer/rules/logical/FoldNull.java index d60cb130f37b7..5032d4a333cc6 100644 --- a/x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/optimizer/rules/logical/FoldNull.java +++ b/x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/optimizer/rules/logical/FoldNull.java @@ -46,6 +46,9 @@ public Expression rule(Expression e, LogicalOptimizerContext ctx) { // Non-evaluatable functions stay as a STATS grouping (It isn't moved to an early EVAL like other groupings), // so folding it to null would currently break the plan, as we don't create an attribute/channel for that null value. && e instanceof GroupingFunction.NonEvaluatableGroupingFunction == false + // We cannot fold aggregate functions until we resolve https://github.com/elastic/elasticsearch/issues/100634. + // AggregateMapper cannot handle aggregate functions with literal values. + && e instanceof AggregateFunction == false && Expressions.anyMatch(e.children(), Expressions::isGuaranteedNull)) { return Literal.of(e, null); } diff --git a/x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/optimizer/rules/logical/ReplaceStatsFilteredAggWithEval.java b/x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/optimizer/rules/logical/ReplaceStatsFilteredOrNullAggWithEval.java similarity index 86% rename from x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/optimizer/rules/logical/ReplaceStatsFilteredAggWithEval.java rename to x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/optimizer/rules/logical/ReplaceStatsFilteredOrNullAggWithEval.java index 82d9e00f2b479..6ccb31dd8ce8a 100644 --- a/x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/optimizer/rules/logical/ReplaceStatsFilteredAggWithEval.java +++ b/x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/optimizer/rules/logical/ReplaceStatsFilteredOrNullAggWithEval.java @@ -15,6 +15,7 @@ import org.elasticsearch.xpack.esql.core.expression.Literal; import org.elasticsearch.xpack.esql.core.expression.NamedExpression; import org.elasticsearch.xpack.esql.core.tree.Source; +import org.elasticsearch.xpack.esql.core.type.DataType; import org.elasticsearch.xpack.esql.core.util.Holder; import org.elasticsearch.xpack.esql.expression.function.aggregate.Absent; import org.elasticsearch.xpack.esql.expression.function.aggregate.AggregateFunction; @@ -34,11 +35,20 @@ import java.util.List; /** - * Replaces an aggregation function having a false/null filter with an EVAL node. + * Replaces an aggregation function with an EVAL node under 2 conditions. + * + * First, having a false/null filter * 
  *     ... | STATS/INLINE STATS x = someAgg(y) WHERE FALSE {BY z} | ...
  *     =>
- *     ... | STATS/INLINE STATS x = someAgg(y) {BY z} > | EVAL x = NULL | KEEP x{, z} | ...
+ *     ... | EVAL x = NULL | KEEP x{, z} | ...
+ *
+ * + * Second, having an agg on a null value + * 
+ *     ... | STATS/INLINE STATS x = someAgg(null) {BY z} | ...
+ *     =>
+ *     ... | EVAL x = NULL | KEEP x{, z} | ...
  *
* * This rule is applied to both STATS' {@link Aggregate} and {@link InlineJoin} right-hand side {@link Aggregate} plans. @@ -46,7 +56,9 @@ * its right-hand side {@link Aggregate}. * Skipped in local optimizer: once a fragment contains an Agg, this can no longer be pruned, which the rule can do */ -public class ReplaceStatsFilteredAggWithEval extends OptimizerRules.OptimizerRule implements OptimizerRules.CoordinatorOnly { +public class ReplaceStatsFilteredOrNullAggWithEval extends OptimizerRules.OptimizerRule + implements + OptimizerRules.CoordinatorOnly { @Override protected LogicalPlan rule(LogicalPlan plan) { Aggregate aggregate; @@ -69,11 +81,7 @@ protected LogicalPlan rule(LogicalPlan plan) { List newProjections = new ArrayList<>(oldAggSize); for (var ne : aggregate.aggregates()) { - if (ne instanceof Alias alias - && alias.child() instanceof AggregateFunction aggFunction - && aggFunction.hasFilter() - && aggFunction.filter() instanceof Literal literal - && Boolean.FALSE.equals(literal.value())) { + if (ne instanceof Alias alias && alias.child() instanceof AggregateFunction aggFunction && shouldReplace(aggFunction)) { Object value = mapNullToValue(aggFunction); Alias newAlias = alias.replaceChild(Literal.of(aggFunction, value)); @@ -119,6 +127,14 @@ protected LogicalPlan rule(LogicalPlan plan) { return plan; } + private static boolean shouldReplace(AggregateFunction aggFunction) { + return hasFalseFilter(aggFunction) || DataType.isNull(aggFunction.field().dataType()); + } + + private static boolean hasFalseFilter(AggregateFunction aggFunction) { + return aggFunction.hasFilter() && aggFunction.filter() instanceof Literal literal && Boolean.FALSE.equals(literal.value()); + } + private static Object mapNullToValue(AggregateFunction aggFunction) { return switch (aggFunction) { case Count ignored -> 0L; diff --git a/x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/optimizer/LogicalPlanOptimizerTests.java b/x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/optimizer/LogicalPlanOptimizerTests.java index 40d2bb362dedb..9a4a18e735ada 100644 --- a/x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/optimizer/LogicalPlanOptimizerTests.java +++ b/x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/optimizer/LogicalPlanOptimizerTests.java @@ -21,6 +21,7 @@ import org.elasticsearch.core.Tuple; import org.elasticsearch.dissect.DissectParser; import org.elasticsearch.index.IndexMode; +import org.elasticsearch.test.junit.annotations.TestLogging; import org.elasticsearch.xpack.esql.EsqlTestUtils; import org.elasticsearch.xpack.esql.VerificationException; import org.elasticsearch.xpack.esql.action.EsqlCapabilities; @@ -231,7 +232,7 @@ import static org.hamcrest.Matchers.not; import static org.hamcrest.Matchers.startsWith; -//@TestLogging(value = "org.elasticsearch.xpack.esql:TRACE", reason = "debug") +@TestLogging(value = "org.elasticsearch.xpack.esql:TRACE", reason = "debug") public class LogicalPlanOptimizerTests extends AbstractLogicalPlanOptimizerTests { private static final LiteralsOnTheRight LITERALS_ON_THE_RIGHT = new LiteralsOnTheRight(); diff --git a/x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/optimizer/rules/logical/FoldNullTests.java b/x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/optimizer/rules/logical/FoldNullTests.java index 6c4ed87e9d8d3..3931cf9fccce1 100644 --- a/x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/optimizer/rules/logical/FoldNullTests.java +++ b/x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/optimizer/rules/logical/FoldNullTests.java @@ -23,8 +23,8 @@ import org.elasticsearch.xpack.esql.expression.function.aggregate.MedianAbsoluteDeviation; import org.elasticsearch.xpack.esql.expression.function.aggregate.Min; import org.elasticsearch.xpack.esql.expression.function.aggregate.Percentile; -import org.elasticsearch.xpack.esql.expression.function.aggregate.SpatialCentroid; import org.elasticsearch.xpack.esql.expression.function.aggregate.Sum; +import org.elasticsearch.xpack.esql.expression.function.aggregate.Values; import org.elasticsearch.xpack.esql.expression.function.grouping.Bucket; import org.elasticsearch.xpack.esql.expression.function.grouping.Categorize; import org.elasticsearch.xpack.esql.expression.function.scalar.convert.ToString; @@ -158,8 +158,6 @@ public void testGenericNullableExpression() { assertNullLiteral(foldNull(new Cos(EMPTY, NULL))); // string functions assertNullLiteral(foldNull(new LTrim(EMPTY, NULL))); - // spatial - assertNullLiteral(foldNull(new SpatialCentroid(EMPTY, NULL))); // ip assertNullLiteral(foldNull(new CIDRMatch(EMPTY, NULL, List.of(NULL)))); // conversion @@ -180,50 +178,34 @@ public void testNullFoldingDoesNotApplyOnLogicalExpressions() { @SuppressWarnings("unchecked") public void testNullFoldingDoesNotApplyOnAggregate() throws Exception { - List> items = List.of(Max.class, Min.class); + List> items = List.of( + Avg.class, + Count.class, + Max.class, + Median.class, + MedianAbsoluteDeviation.class, + Min.class, + Sum.class, + Values.class + ); for (Class clazz : items) { Constructor ctor = clazz.getConstructor(Source.class, Expression.class); AggregateFunction conditionalFunction = ctor.newInstance(EMPTY, getFieldAttribute("a")); assertEquals(conditionalFunction, foldNull(conditionalFunction)); conditionalFunction = ctor.newInstance(EMPTY, NULL); - assertEquals(NULL, foldNull(conditionalFunction)); + assertEquals(conditionalFunction, foldNull(conditionalFunction)); } - Avg avg = new Avg(EMPTY, getFieldAttribute("a")); - assertEquals(avg, foldNull(avg)); - avg = new Avg(EMPTY, NULL); - assertEquals(new Literal(EMPTY, null, DOUBLE), foldNull(avg)); - - Count count = new Count(EMPTY, getFieldAttribute("a")); - assertEquals(count, foldNull(count)); - count = new Count(EMPTY, NULL); - assertEquals(count, foldNull(count)); - CountDistinct countd = new CountDistinct(EMPTY, getFieldAttribute("a"), getFieldAttribute("a")); assertEquals(countd, foldNull(countd)); countd = new CountDistinct(EMPTY, NULL, NULL); - assertEquals(new Literal(EMPTY, null, LONG), foldNull(countd)); - - Median median = new Median(EMPTY, getFieldAttribute("a")); - assertEquals(median, foldNull(median)); - median = new Median(EMPTY, NULL); - assertEquals(new Literal(EMPTY, null, DOUBLE), foldNull(median)); - - MedianAbsoluteDeviation medianad = new MedianAbsoluteDeviation(EMPTY, getFieldAttribute("a")); - assertEquals(medianad, foldNull(medianad)); - medianad = new MedianAbsoluteDeviation(EMPTY, NULL); - assertEquals(new Literal(EMPTY, null, DOUBLE), foldNull(medianad)); + assertEquals(countd, foldNull(countd)); Percentile percentile = new Percentile(EMPTY, getFieldAttribute("a"), getFieldAttribute("a")); assertEquals(percentile, foldNull(percentile)); percentile = new Percentile(EMPTY, NULL, NULL); - assertEquals(new Literal(EMPTY, null, DOUBLE), foldNull(percentile)); - - Sum sum = new Sum(EMPTY, getFieldAttribute("a")); - assertEquals(sum, foldNull(sum)); - sum = new Sum(EMPTY, NULL); - assertEquals(new Literal(EMPTY, null, DOUBLE), foldNull(sum)); + assertEquals(percentile, foldNull(percentile)); } public void testNullFoldableDoesNotApplyToIsNullAndNotNull() { diff --git a/x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/optimizer/rules/logical/ReplaceStatsFilteredAggWithEvalTests.java b/x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/optimizer/rules/logical/ReplaceStatsFilteredOrNullAggWithEvalTests.java similarity index 91% rename from x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/optimizer/rules/logical/ReplaceStatsFilteredAggWithEvalTests.java rename to x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/optimizer/rules/logical/ReplaceStatsFilteredOrNullAggWithEvalTests.java index c6ff818246e38..491dde69d2304 100644 --- a/x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/optimizer/rules/logical/ReplaceStatsFilteredAggWithEvalTests.java +++ b/x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/optimizer/rules/logical/ReplaceStatsFilteredOrNullAggWithEvalTests.java @@ -32,6 +32,7 @@ import static org.elasticsearch.xpack.esql.EsqlTestUtils.as; import static org.elasticsearch.xpack.esql.core.type.DataType.INTEGER; import static org.elasticsearch.xpack.esql.core.type.DataType.LONG; +import static org.elasticsearch.xpack.esql.core.type.DataType.NULL; import static org.elasticsearch.xpack.esql.optimizer.LogicalPlanOptimizerTests.releaseBuildForInlineStats; import static org.hamcrest.Matchers.contains; import static org.hamcrest.Matchers.containsString; @@ -39,7 +40,7 @@ import static org.hamcrest.Matchers.nullValue; import static org.hamcrest.Matchers.startsWith; -public class ReplaceStatsFilteredAggWithEvalTests extends AbstractLogicalPlanOptimizerTests { +public class ReplaceStatsFilteredOrNullAggWithEvalTests extends AbstractLogicalPlanOptimizerTests { /** * 
{@code
@@ -800,4 +801,85 @@ public void testReplaceTwoConsecutiveInlineStats_WithFalseFilters() {
         assertThat(aliasCc.child().fold(FoldContext.small()), is(0L));
         as(eval.child(), EsRelation.class);
     }
+
+    /**
+     * 
{@code
+     * Limit[1000[INTEGER],false,false]
+     * \_LocalRelation[[max(x){r}#6],Page{blocks=[ConstantNullBlock[positions=1]]}]
+     * }

+     */
+    public void testReplaceStatsMaxOnNullReferenceWithEvalSingleAgg() {
+        var plan = plan("""
+            row x = null
+            | stats max(x)
+            """);
+
+        var project = as(plan, Limit.class);
+        var source = as(project.child(), LocalRelation.class);
+        assertThat(Expressions.names(source.output()), contains("max(x)"));
+        Page page = source.supplier().get();
+        assertThat(page.getBlockCount(), is(1));
+        assertThat(page.getBlock(0).getPositionCount(), is(1));
+        assertTrue(page.getBlock(0).areAllValuesNull());
+    }
+
+    /**
+     * 
{@code
+     * Project[[y{r}#6]]
+     * \_Eval[[null[NULL] AS y#6]]
+     *   \_Limit[1000[INTEGER],false,false]
+     *     \_LocalRelation[[{e}#7],Page{blocks=[ConstantNullBlock[positions=1]]}]
+     * }

+     */
+    public void testReplaceStatsMaxOnNullLiteralWithEvalSingleAgg() {
+        var plan = plan("""
+            row x = 3
+            | stats y = max(null)
+            """);
+
+        var project = as(plan, Project.class);
+        assertThat(Expressions.names(project.projections()), contains("y"));
+        var eval = as(project.child(), Eval.class);
+        assertThat(eval.fields().size(), is(1));
+
+        var alias = as(eval.fields().getFirst(), Alias.class);
+        assertTrue(alias.child().foldable());
+        assertThat(alias.child().fold(FoldContext.small()), nullValue());
+        assertThat(alias.child().dataType(), is(NULL));
+
+        var limit = as(eval.child(), Limit.class);
+        var source = as(limit.child(), LocalRelation.class);
+    }
+
+    /**
+     * 
{@code
+     * Project[[max(x){r}#9, sum(y){r}#11, x{r}#4]]
+     * \_Eval[[null[NULL] AS max(x)#9]]
+     *   \_Limit[1000[INTEGER],false,false]
+     *     \_Aggregate[[x{r}#4],[SUM(y{r}#6,true[BOOLEAN],PT0S[TIME_DURATION],compensated[KEYWORD]) AS sum(y)#11, x{r}#4]]
+     *       \_LocalRelation[[x{r}#4, y{r}#6],Page{blocks=[ConstantNullBlock[positions=1], IntVectorBlock[vector=..]]}]
+     * }

+     */
+    public void testReplaceStatsMaxOnNullWithEvalAndAgg() {
+        var plan = plan("""
+            row x = null, y = 1
+            | stats max(x),
+                    sum(y)
+              by x
+            """);
+
+        var project = as(plan, Project.class);
+        assertThat(Expressions.names(project.projections()), contains("max(x)", "sum(y)", "x"));
+        var eval = as(project.child(), Eval.class);
+        assertThat(eval.fields().size(), is(1));
+
+        var alias = as(eval.fields().getFirst(), Alias.class);
+        assertTrue(alias.child().foldable());
+        assertThat(alias.child().fold(FoldContext.small()), nullValue());
+        assertThat(alias.child().dataType(), is(NULL));
+
+        var limit = as(eval.child(), Limit.class);
+        var aggregate = as(limit.child(), Aggregate.class);
+        var source = as(aggregate.child(), LocalRelation.class);
+    }
 }

From 0be6364faaab889a972e80c249e0c7a2c72a40c5 Mon Sep 17 00:00:00 2001
From: Dimitris Athanasiou 
Date: Fri, 19 Dec 2025 12:29:55 +0200
Subject: [PATCH 2/2] Update docs/changelog/139797.yaml

---
 docs/changelog/139797.yaml | 6 ++++++
 1 file changed, 6 insertions(+)
 create mode 100644 docs/changelog/139797.yaml

diff --git a/docs/changelog/139797.yaml b/docs/changelog/139797.yaml
new file mode 100644
index 0000000000000..be96b176032cf
--- /dev/null
+++ b/docs/changelog/139797.yaml
@@ -0,0 +1,6 @@
+pr: 139797
+summary: Fix aggregation on null value
+area: ES|QL
+type: bug
+issues:
+ - 137544