ES|QL: Fix wrong pruning of plans with no output columns

docs/changelog/133405.yaml

@@ -0,0 +1,5 @@
+pr: 133405
+summary: Fix wrong pruning of plans with no output columns
+area: ES|QL
+type: bug
+issues: []

server/src/main/java/org/elasticsearch/TransportVersions.java

@@ -368,6 +368,7 @@ static TransportVersion def(int id) {
     public static final TransportVersion DATA_STREAM_WRITE_INDEX_ONLY_SETTINGS = def(9_142_0_00);
     public static final TransportVersion SCRIPT_RESCORER = def(9_143_0_00);
     public static final TransportVersion ESQL_LOOKUP_OPERATOR_EMITTED_ROWS = def(9_144_0_00);
+    public static final TransportVersion ESQL_PLAN_WITH_NO_COLUMNS = def(9_145_0_00);
 
     /*
      * STOP! READ THIS FIRST! No, really,

x-pack/plugin/esql/qa/testFixtures/src/main/java/org/elasticsearch/xpack/esql/EsqlTestUtils.java

@@ -34,6 +34,7 @@
 import org.elasticsearch.compute.data.DoubleBlock;
 import org.elasticsearch.compute.data.IntBlock;
 import org.elasticsearch.compute.data.LongBlock;
+import org.elasticsearch.compute.data.Page;
 import org.elasticsearch.core.PathUtils;
 import org.elasticsearch.core.SuppressForbidden;
 import org.elasticsearch.core.Tuple;
@@ -475,7 +476,11 @@ public static LogicalPlan emptySource() {
     }
 
     public static LogicalPlan localSource(BlockFactory blockFactory, List<Attribute> fields, List<Object> row) {
-        return new LocalRelation(Source.EMPTY, fields, LocalSupplier.of(BlockUtils.fromListRow(blockFactory, row)));
+        return new LocalRelation(
+            Source.EMPTY,
+            fields,
+            LocalSupplier.of(row.isEmpty() ? new Page(0) : new Page(BlockUtils.fromListRow(blockFactory, row)))
+        );
     }
 
     public static <T> T as(Object node, Class<T> type) {

x-pack/plugin/esql/qa/testFixtures/src/main/resources/drop.csv-spec

@@ -49,29 +49,136 @@ b:integer | x:integer
 ;
 
 dropAllColumns
+required_capability: fix_no_columns
 from employees | keep height | drop height | eval x = 1;
 
 x:integer
+1
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 ;
 
 dropAllColumns_WithLimit
+required_capability: fix_no_columns
 from employees | keep height | drop height | eval x = 1 | limit 3;
 
 x:integer
+1
+1
+1
 ;
 
 dropAllColumns_WithCount
+required_capability: fix_no_columns
 from employees | keep height | drop height | eval x = 1 | stats c=count(x);
 
 c:long
-0
+100
 ;
 
 dropAllColumns_WithStats
+required_capability: fix_no_columns
 from employees | keep height | drop height | eval x = 1 | stats c=count(x), mi=min(x), s=sum(x);
 
-c:l|mi:i|s:l
-0  |null|null
+c:l  | mi:i | s:l
+100  | 1    | 100
 ;
 
 

x-pack/plugin/esql/src/internalClusterTest/java/org/elasticsearch/xpack/esql/action/CrossClusterLookupJoinIT.java

@@ -437,7 +437,7 @@ public void testLookupJoinEmptyIndex() throws IOException {
         setSkipUnavailable(REMOTE_CLUSTER_1, randomBoolean());
 
         Exception ex;
-        for (String index : List.of("values_lookup", "values_lookup_map", "values_lookup_map_lookup")) {
+        for (String index : List.of("values_lookup", "values_lookup_map_lookup")) {
             ex = expectThrows(
                 VerificationException.class,
                 () -> runQuery("FROM logs-* | LOOKUP JOIN " + index + " ON v | KEEP v", randomBoolean())
@@ -449,6 +449,29 @@ public void testLookupJoinEmptyIndex() throws IOException {
             );
             assertThat(ex.getMessage(), containsString("Unknown column [v] in right side of join"));
         }
+
+        ex = expectThrows(
+            VerificationException.class,
+            () -> runQuery("FROM logs-* | LOOKUP JOIN values_lookup_map ON v | KEEP v", randomBoolean())
+        );
+        assertThat(
+            ex.getMessage(),
+            containsString(
+                "Lookup Join requires a single lookup mode index; "
+                    + "[values_lookup_map] resolves to [values_lookup_map] in [standard] mode"
+            )
+        );
+        ex = expectThrows(
+            VerificationException.class,
+            () -> runQuery("FROM c*:logs-* | LOOKUP JOIN values_lookup_map ON v | KEEP v", randomBoolean())
+        );
+        assertThat(
+            ex.getMessage(),
+            containsString(
+                "Lookup Join requires a single lookup mode index; "
+                    + "[values_lookup_map] resolves to [cluster-a:values_lookup_map] in [standard] mode"
+            )
+        );
     }
 
     public void testLookupJoinIndexMode() throws IOException {

x-pack/plugin/esql/src/internalClusterTest/java/org/elasticsearch/xpack/esql/action/EsqlActionIT.java

@@ -951,15 +951,15 @@ public void testDropAllColumns() {
             logger.info(results);
             assertThat(results.columns(), hasSize(1));
             assertThat(results.columns(), contains(new ColumnInfoImpl("a", "integer", null)));
-            assertThat(getValuesList(results), is(empty()));
+            assertThat(getValuesList(results).size(), is(40));
         }
     }
 
     public void testDropAllColumnsWithStats() {
         try (EsqlQueryResponse results = run("from test | stats g = count(data) | drop g")) {
             logger.info(results);
             assertThat(results.columns(), is(empty()));
-            assertThat(getValuesList(results), is(empty()));
+            assertThat(getValuesList(results).size(), is(1));
         }
     }
 

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/action/EsqlCapabilities.java

@@ -1389,7 +1389,13 @@ public enum Cap {
         /**
          * Support for vector Hamming distance.
          */
-        HAMMING_VECTOR_SIMILARITY_FUNCTION(Build.current().isSnapshot());
+        HAMMING_VECTOR_SIMILARITY_FUNCTION(Build.current().isSnapshot()),
+
+        /**
+         * Fix management of plans with no columns
+         * https://github.com/elastic/elasticsearch/issues/120272
+         */
+        FIX_NO_COLUMNS;
 
         private final boolean enabled;
 

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/analysis/Analyzer.java

@@ -12,6 +12,7 @@
 import org.elasticsearch.common.lucene.BytesRefs;
 import org.elasticsearch.compute.data.AggregateMetricDoubleBlockBuilder;
 import org.elasticsearch.compute.data.Block;
+import org.elasticsearch.compute.data.Page;
 import org.elasticsearch.core.Strings;
 import org.elasticsearch.index.IndexMode;
 import org.elasticsearch.logging.Logger;
@@ -458,7 +459,7 @@ private LocalRelation tableMapAsRelation(Source source, Map<String, Column> mapT
                 // prepare the block for the supplier
                 blocks[i++] = column.values();
             }
-            LocalSupplier supplier = LocalSupplier.of(blocks);
+            LocalSupplier supplier = LocalSupplier.of(blocks.length > 0 ? new Page(blocks) : new Page(0));
             return new LocalRelation(source, attributes, supplier);
         }
     }

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/expression/predicate/Predicates.java

@@ -145,6 +145,9 @@ public static Tuple<Expression, List<Expression>> extractCommon(List<Expression>
             }
             splitAnds.add(split);
         }
+        if (common == null) {
+            common = List.of();
+        }
 
         List<Expression> trimmed = new ArrayList<>(expressions.size());
         final List<Expression> finalCommon = common;

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/optimizer/LogicalPlanOptimizer.java

@@ -28,7 +28,7 @@
 import org.elasticsearch.xpack.esql.optimizer.rules.logical.PropagateNullable;
 import org.elasticsearch.xpack.esql.optimizer.rules.logical.PropgateUnmappedFields;
 import org.elasticsearch.xpack.esql.optimizer.rules.logical.PruneColumns;
-import org.elasticsearch.xpack.esql.optimizer.rules.logical.PruneEmptyPlans;
+import org.elasticsearch.xpack.esql.optimizer.rules.logical.PruneEmptyAggregates;
 import org.elasticsearch.xpack.esql.optimizer.rules.logical.PruneFilters;
 import org.elasticsearch.xpack.esql.optimizer.rules.logical.PruneLiteralsInOrderBy;
 import org.elasticsearch.xpack.esql.optimizer.rules.logical.PruneRedundantOrderBy;
@@ -166,7 +166,6 @@ protected static Batch<LogicalPlan> operators(boolean local) {
             "Operator Optimization",
             new CombineProjections(local),
             new CombineEvals(),
-            new PruneEmptyPlans(),
             new PropagateEmptyRelation(),
             new FoldNull(),
             new SplitInWithFoldableValue(),
@@ -203,7 +202,8 @@ protected static Batch<LogicalPlan> operators(boolean local) {
             new PushDownAndCombineOrderBy(),
             new PruneRedundantOrderBy(),
             new PruneRedundantSortClauses(),
-            new PruneLeftJoinOnNullMatchingField()
+            new PruneLeftJoinOnNullMatchingField(),
+            new PruneEmptyAggregates()
         );
     }
 

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/optimizer/rules/logical/PropagateEmptyRelation.java

@@ -10,6 +10,7 @@
 import org.elasticsearch.compute.data.Block;
 import org.elasticsearch.compute.data.BlockFactory;
 import org.elasticsearch.compute.data.BlockUtils;
+import org.elasticsearch.compute.data.Page;
 import org.elasticsearch.xpack.esql.EsqlIllegalArgumentException;
 import org.elasticsearch.xpack.esql.core.expression.Alias;
 import org.elasticsearch.xpack.esql.core.expression.FoldContext;
@@ -41,7 +42,10 @@ protected LogicalPlan rule(UnaryPlan plan, LogicalOptimizerContext ctx) {
             // only care about non-grouped aggs might return something (count)
             if (plan instanceof Aggregate agg && agg.groupings().isEmpty()) {
                 List<Block> emptyBlocks = aggsFromEmpty(ctx.foldCtx(), agg.aggregates());
-                p = replacePlanByRelation(plan, LocalSupplier.of(emptyBlocks.toArray(Block[]::new)));
+                p = replacePlanByRelation(
+                    plan,
+                    LocalSupplier.of(emptyBlocks.isEmpty() ? new Page(0) : new Page(emptyBlocks.toArray(Block[]::new)))
+                );
             } else {
                 p = PruneEmptyPlans.skipPlan(plan);
             }

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/optimizer/rules/logical/PruneColumns.java

@@ -7,8 +7,8 @@
 
 package org.elasticsearch.xpack.esql.optimizer.rules.logical;
 
-import org.elasticsearch.compute.data.Block;
 import org.elasticsearch.compute.data.BlockUtils;
+import org.elasticsearch.compute.data.Page;
 import org.elasticsearch.index.IndexMode;
 import org.elasticsearch.xpack.esql.core.expression.Alias;
 import org.elasticsearch.xpack.esql.core.expression.Attribute;
@@ -111,7 +111,7 @@ private static LogicalPlan pruneColumnsInAggregate(Aggregate aggregate, Attribut
                 p = new LocalRelation(
                     aggregate.source(),
                     List.of(Expressions.attribute(aggregate.aggregates().getFirst())),
-                    LocalSupplier.of(new Block[] { BlockUtils.constantBlock(PlannerUtils.NON_BREAKING_BLOCK_FACTORY, null, 1) })
+                    LocalSupplier.of(new Page(BlockUtils.constantBlock(PlannerUtils.NON_BREAKING_BLOCK_FACTORY, null, 1)))
                 );
             } else {
                 // Aggs cannot produce pages with 0 columns, so retain one grouping.

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/optimizer/rules/logical/PruneEmptyAggregates.java

@@ -0,0 +1,27 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
+package org.elasticsearch.xpack.esql.optimizer.rules.logical;
+
+import org.elasticsearch.compute.data.Page;
+import org.elasticsearch.xpack.esql.plan.logical.Aggregate;
+import org.elasticsearch.xpack.esql.plan.logical.LogicalPlan;
+import org.elasticsearch.xpack.esql.plan.logical.local.LocalRelation;
+import org.elasticsearch.xpack.esql.plan.logical.local.LocalSupplier;
+
+import java.util.List;
+
+public final class PruneEmptyAggregates extends OptimizerRules.OptimizerRule<Aggregate> {
+    @Override
+    protected LogicalPlan rule(Aggregate agg) {
+        if (agg.aggregates().isEmpty() && agg.groupings().isEmpty()) {
+            return new LocalRelation(agg.source(), List.of(), LocalSupplier.of(new Page(1)));
+        }
+        return agg;
+    }
+
+}

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/optimizer/rules/logical/ReplaceRowAsLocalRelation.java

@@ -8,6 +8,7 @@
 package org.elasticsearch.xpack.esql.optimizer.rules.logical;
 
 import org.elasticsearch.compute.data.BlockUtils;
+import org.elasticsearch.compute.data.Page;
 import org.elasticsearch.xpack.esql.optimizer.LogicalOptimizerContext;
 import org.elasticsearch.xpack.esql.plan.logical.LogicalPlan;
 import org.elasticsearch.xpack.esql.plan.logical.Row;
@@ -29,6 +30,6 @@ protected LogicalPlan rule(Row row, LogicalOptimizerContext context) {
         List<Object> values = new ArrayList<>(fields.size());
         fields.forEach(f -> values.add(f.child().fold(context.foldCtx())));
         var blocks = BlockUtils.fromListRow(PlannerUtils.NON_BREAKING_BLOCK_FACTORY, values);
-        return new LocalRelation(row.source(), row.output(), new CopyingLocalSupplier(blocks));
+        return new LocalRelation(row.source(), row.output(), new CopyingLocalSupplier(blocks.length == 0 ? new Page(0) : new Page(blocks)));
     }
 }