remove subquery merging in parser, add tests for subqueries with request filter

Author: fang-xing-esql

x-pack/plugin/esql/qa/server/src/main/java/org/elasticsearch/xpack/esql/qa/rest/RestEsqlTestCase.java

@@ -1317,6 +1317,23 @@ public void testTopLevelFilterBoolMerged() throws IOException {
         }
     }
 
+    public void testTopLevelFilterWithSubqueriesInFromCommand() throws IOException {
+        bulkLoadTestData(10);
+
+        String query = format(null, "FROM {} , (FROM {} | WHERE integer < 8) | STATS count(*)", testIndexName(), testIndexName());
+
+        RequestObjectBuilder builder = requestObjectBuilder().filter(b -> {
+            b.startObject("range");
+            {
+                b.startObject("integer").field("gte", "5").endObject();
+            }
+            b.endObject();
+        }).query(query);
+
+        Map<String, Object> result = runEsql(builder);
+        assertResultMap(result, matchesList().item(matchesMap().entry("name", "count(*)").entry("type", "long")), List.of(List.of(8)));
+    }
+
     private static String queryWithComplexFieldNames(int field) {
         StringBuilder query = new StringBuilder();
         query.append(" | keep ").append(randomAlphaOfLength(10)).append(1);

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

@@ -2,7 +2,7 @@
 // CSV spec for subqueries
 //
 
-subqueryInFromMergeToMainIndexPattern
+subqueryInFrom
 required_capability: fork_v9
 required_capability: subquery_in_from_command
 
@@ -25,6 +25,25 @@ null           | null              | 172.21.3.15
 null           | null              | 172.21.3.15
 ;
 
+subqueryInFromWithIdenticalIndexPatternsInMainAndSubquery
+required_capability: fork_v9
+required_capability: subquery_in_from_command
+
+FROM employees, (FROM employees)
+| WHERE emp_no >= 10091 AND emp_no < 10094
+| SORT emp_no
+| KEEP  emp_no, languages
+;
+
+emp_no:integer | languages:integer
+10091          | 3
+10091          | 3
+10092          | 1
+10092          | 1
+10093          | 3
+10093          | 3
+;
+
 subqueryInFromWithEvalInSubquery
 required_capability: fork_v9
 required_capability: subquery_in_from_command

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

@@ -116,10 +116,6 @@ private void collectSubqueryIndexPattern(
         Set<IndexPattern> subqueryIndices,
         IndexPattern mainIndexPattern
     ) {
-        if (relation.preAnalyzed()) {
-            return;
-        }
-
         IndexPattern pattern = relation.indexPattern();
         boolean isLookup = relation.indexMode() == IndexMode.LOOKUP;
         boolean isMainIndexPattern = pattern == mainIndexPattern;

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/parser/LogicalPlanBuilder.java

@@ -356,58 +356,24 @@ private LogicalPlan visitRelation(Source source, IndexMode indexMode, EsqlBasePa
             if (indexMode == IndexMode.TIME_SERIES) {
                 throw new ParsingException(source, "Subqueries are not supported in TS command");
             }
-            // If the subquery has only from command, combine the subquery index patterns into the main index pattern
-            // from idx1, idx2, (from idx3), (from idx4) => from idx1, idx2, idx3, idx4
-            List<Subquery> remainingSubqueries = new ArrayList<>(subqueries.size());
-            for (Subquery subquery : subqueries) {
-                String subqueryIndexPattern = getIndexPatternIfOnlyFrom(subquery);
-                boolean canCombine = subqueryIndexPattern != null && metadataFields.isEmpty();
-                if (canCombine) {
-                    // the subquery has only from command without metadata fields, combine the index patterns
-                    // as how or whether combining metadata fields is unclear yet
-                    String existingIndexPattern = table.indexPattern();
-                    String combinedPattern = existingIndexPattern.isEmpty()
-                        ? subqueryIndexPattern
-                        : existingIndexPattern + "," + subqueryIndexPattern;
-                    table = new IndexPattern(table.source(), combinedPattern);
-                    unresolvedRelation = new UnresolvedRelation(source, table, false, metadataFields, indexMode, null, commandName);
-                } else {
-                    remainingSubqueries.add(subquery);
-                }
-            }
-
-            if (remainingSubqueries.isEmpty()) {
-                return unresolvedRelation;
-            }
 
-            List<LogicalPlan> mainQueryAndSubqueries = new ArrayList<>(remainingSubqueries.size() + 1);
+            List<LogicalPlan> mainQueryAndSubqueries = new ArrayList<>(subqueries.size() + 1);
             if (table.indexPattern().isEmpty() == false) {
                 mainQueryAndSubqueries.add(unresolvedRelation);
                 telemetryAccounting(unresolvedRelation);
             }
-            mainQueryAndSubqueries.addAll(remainingSubqueries);
+            mainQueryAndSubqueries.addAll(subqueries);
 
             if (mainQueryAndSubqueries.size() == 1) {
                 // if there is only one child, return it directly, no need for UnionAll
-                return table.indexPattern().isEmpty() ? remainingSubqueries.get(0).plan() : unresolvedRelation;
+                return table.indexPattern().isEmpty() ? subqueries.get(0).plan() : unresolvedRelation;
             } else {
                 // the output of UnionAll is resolved by analyzer
                 return new UnionAll(source, mainQueryAndSubqueries, List.of());
             }
         }
     }
 
-    /**
-     * If the subquery plan is only a from command, return the index pattern; otherwise return null.
-     */
-    private String getIndexPatternIfOnlyFrom(Subquery subquery) {
-        LogicalPlan plan = subquery.plan();
-        if (plan instanceof UnresolvedRelation ur) {
-            return ur.indexPattern().indexPattern();
-        }
-        return null;
-    }
-
     private List<Subquery> visitSubqueriesInFromCommand(List<EsqlBaseParser.SubqueryContext> ctxs) {
         if (EsqlCapabilities.Cap.SUBQUERY_IN_FROM_COMMAND.isEnabled() == false) {
             return List.of();