ESQL: Validate unique plan attribute names

docs/changelog/110488.yaml

@@ -0,0 +1,5 @@
+pr: 110488
+summary: "ESQL: Validate unique plan attribute names"
+area: ES|QL
+type: bug
+issues: []

x-pack/plugin/esql-core/src/main/java/org/elasticsearch/xpack/esql/core/analyzer/AnalyzerRules.java

@@ -20,8 +20,6 @@
 import java.util.function.Predicate;
 import java.util.function.Supplier;
 
-import static java.util.Collections.singletonList;
-
 public final class AnalyzerRules {
 
     public abstract static class AnalyzerRule<SubPlan extends LogicalPlan> extends Rule<SubPlan, LogicalPlan> {
@@ -138,14 +136,6 @@ public static List<Attribute> maybeResolveAgainstList(
             )
             .toList();
 
-        return singletonList(
-            ua.withUnresolvedMessage(
-                "Reference ["
-                    + ua.qualifiedName()
-                    + "] is ambiguous (to disambiguate use quotes or qualifiers); "
-                    + "matches any of "
-                    + refs
-            )
-        );
+        throw new IllegalStateException("Reference [" + ua.qualifiedName() + "] is ambiguous; " + "matches any of " + refs);
     }
 }

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

@@ -69,13 +69,6 @@ a:integer | b:integer | c:null | z:integer
 1 | 2 | null | null
 ;
 
-evalRowWithNull2
-row a = 1, null, b = 2, c = null, null | eval z = a+b;
-
-a:integer | null:null | b:integer | c:null | null:null | z:integer
-1 | null | 2 | null | null | 3
-;
-
 evalRowWithNull3
 row a = 1, b = 2, x = round(null) | eval z = a+b+x;
 

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

@@ -46,6 +46,7 @@
 import java.util.ArrayList;
 import java.util.BitSet;
 import java.util.Collection;
+import java.util.HashSet;
 import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Set;
@@ -349,10 +350,15 @@ private static void checkRegexExtractOnlyOnStrings(LogicalPlan p, Set<Failure> f
 
     private static void checkRow(LogicalPlan p, Set<Failure> failures) {
         if (p instanceof Row row) {
+            Set<String> outputAttributeNames = new HashSet<>();
+
             row.fields().forEach(a -> {
                 if (EsqlDataTypes.isRepresentable(a.dataType()) == false) {
                     failures.add(fail(a, "cannot use [{}] directly in a row assignment", a.child().sourceText()));
                 }
+                if (outputAttributeNames.add(a.name()) == false) {
+                    failures.add(fail(a, "cannot use the name [{}] multiple times in a row assignment", a.name()));
+                }
             });
         }
     }

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

@@ -8,8 +8,10 @@
 package org.elasticsearch.xpack.esql.optimizer;
 
 import org.elasticsearch.xpack.esql.core.common.Failures;
+import org.elasticsearch.xpack.esql.core.expression.Attribute;
 import org.elasticsearch.xpack.esql.core.expression.AttributeSet;
 import org.elasticsearch.xpack.esql.core.expression.Expressions;
+import org.elasticsearch.xpack.esql.core.expression.NameId;
 import org.elasticsearch.xpack.esql.core.plan.QueryPlan;
 import org.elasticsearch.xpack.esql.core.plan.logical.LogicalPlan;
 import org.elasticsearch.xpack.esql.plan.logical.Aggregate;
@@ -36,6 +38,9 @@
 import org.elasticsearch.xpack.esql.plan.physical.RowExec;
 import org.elasticsearch.xpack.esql.plan.physical.ShowExec;
 
+import java.util.HashSet;
+import java.util.Set;
+
 import static org.elasticsearch.xpack.esql.core.common.Failure.fail;
 
 class OptimizerRules {
@@ -49,9 +54,24 @@ void checkPlan(P p, Failures failures) {
             AttributeSet input = p.inputSet();
             AttributeSet generated = generates(p);
             AttributeSet missing = refs.subtract(input).subtract(generated);
-            if (missing.size() > 0) {
+            if (missing.isEmpty() == false) {
                 failures.add(fail(p, "Plan [{}] optimized incorrectly due to missing references {}", p.nodeString(), missing));
             }
+
+            Set<String> outputAttributeNames = new HashSet<>();
+            Set<NameId> outputAttributeIds = new HashSet<>();
+            for (Attribute outputAttr : p.output()) {
+                if (outputAttributeNames.add(outputAttr.name()) == false || outputAttributeIds.add(outputAttr.id()) == false) {
+                    failures.add(
+                        fail(
+                            p,
+                            "Plan [{}] optimized incorrectly due to duplicate output attribute {}",
+                            p.nodeString(),
+                            outputAttr.toString()
+                        )
+                    );
+                }
+            }
         }
 
         protected AttributeSet references(P p) {

x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/analysis/VerifierTests.java

@@ -35,6 +35,15 @@ public class VerifierTests extends ESTestCase {
     private final Analyzer defaultAnalyzer = AnalyzerTestUtils.expandedDefaultAnalyzer();
     private final Analyzer tsdb = AnalyzerTestUtils.analyzer(AnalyzerTestUtils.tsdbIndexResolution());
 
+    public void testRowAllowsOnlyUniqueAttributeNames() {
+        assertEquals("1:19: cannot use the name [a] multiple times in a row assignment", error("row a = 1, b = 2, a = 3"));
+        assertEquals("1:11: cannot use the name [1] multiple times in a row assignment", error("row 1, 2, 1"));
+        assertEquals(
+            "1:35: cannot use the name [null] multiple times in a row assignment",
+            error("row a = 1, null, b = 2, c = null, null | eval z = a+b")
+        );
+    }
+
     public void testIncompatibleTypesInMathOperation() {
         assertEquals(
             "1:40: second argument of [a + c] must be [datetime or numeric], found value [c] type [keyword]",