more verification tests

Author: jan-elastic

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/approximate/Approximate.java

@@ -251,6 +251,7 @@ private boolean verifyPlan() throws VerificationException {
         // Verify that all commands are supported.
         logicalPlan.forEachUp(plan -> {
             if (SUPPORTED_COMMANDS.contains(plan.getClass()) == false) {
+                // TODO: better way of obtaining the command name
                 throw new VerificationException(
                     List.of(Failure.fail(plan, "query with [" + plan.nodeName().toUpperCase(Locale.ROOT) + "] cannot be approximated"))
                 );
@@ -267,6 +268,7 @@ private boolean verifyPlan() throws VerificationException {
                     plan.transformExpressionsOnly(AggregateFunction.class, aggFn -> {
                         if (SUPPORTED_SINGLE_VALUED_AGGS.contains(aggFn.getClass()) == false
                             && SUPPORTED_MULTIVALUED_AGGS.contains(aggFn.getClass()) == false) {
+                            // TODO: better way of obtaining the agg name
                             throw new VerificationException(
                                 List.of(
                                     Failure.fail(

x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/approximate/ApproximateTests.java

@@ -116,11 +116,23 @@ public void testVerify_validQuery() throws Exception {
         createApproximate("ROW i=[1,2,3] | EVAL x=TO_STRING(i) | DISSECT x \"%{x}\" | STATS i=10*POW(PERCENTILE(i, 0.5), 2) | LIMIT 10");
     }
 
-    public void testVerify_noStats() {
-        assertError("FROM test | EVAL x = 1 | SORT emp_no", equalTo("line 1:1: query without [STATS] cannot be approximated"));
+    public void testVerify_exactlyOneStats() {
+        assertError(
+            "FROM test | EVAL x = 1 | SORT emp_no | LIMIT 100 | MV_EXPAND x",
+            equalTo("line 1:1: query without [STATS] cannot be approximated")
+        );
+        assertError(
+            "FROM test | STATS COUNT() BY emp_no | STATS COUNT()",
+            equalTo("line 1:39: query with multiple [STATS] cannot be approximated")
+        );
     }
 
-    public void testVerify_incompatibleCommand() {
+    public void testVerify_incompatibleSourceCommand() {
+        assertError("SHOW INFO | STATS COUNT()", equalTo("line 1:1: query with [SHOWINFO] cannot be approximated"));
+        assertError("TS test | STATS COUNT(emp_no)", equalTo("line 1:11: query with [TIMESERIESAGGREGATE] cannot be approximated"));
+    }
+
+    public void testVerify_incompatibleProcessingCommand() {
         assertError(
             "FROM test | FORK (EVAL x=1) (EVAL y=1) | STATS COUNT()",
             equalTo("line 1:13: query with [FORK] cannot be approximated")
@@ -138,19 +150,22 @@ public void testVerify_incompatibleCommand() {
             equalTo("line 1:29: query with [INLINESTATS] cannot be approximated")
         );
         assertError(
-            "FROM test | LOOKUP JOIN test_lookup ON emp_no | STATS COUNT()",
+            "FROM test | LOOKUP JOIN test_lookup ON emp_no | FORK (EVAL x=1) (EVAL y=1) | STATS COUNT()",
             equalTo("line 1:13: query with [LOOKUPJOIN] cannot be approximated")
         );
         assertError(
-            "FROM test | STATS emp_no=COUNT() | LOOKUP JOIN test_lookup ON emp_no",
+            "FROM test | STATS emp_no=COUNT() | LOOKUP JOIN test_lookup ON emp_no | FORK (EVAL x=1) (EVAL y=1)",
             equalTo("line 1:36: query with [LOOKUPJOIN] cannot be approximated")
         );
     }
 
     public void testVerify_incompatibleAggregation() {
-        assertError("FROM test | STATS MIN(emp_no)", equalTo("line 1:19: aggregation function [MIN] cannot be approximated"));
         assertError(
-            "FROM test | STATS SUM(emp_no), VALUES(emp_no), COUNT()",
+            "FROM test | SORT emp_no STATS MIN(emp_no) | LIMIT 100",
+            equalTo("line 1:19: aggregation function [MIN] cannot be approximated")
+        );
+        assertError(
+            "FROM test | STATS SUM(emp_no), VALUES(emp_no), TOP(emp_no, 2, \"ASC\"), COUNT()",
             equalTo("line 1:32: aggregation function [VALUES] cannot be approximated")
         );
         assertError(