Tolerate floating point precision in multi node tests (#110238) (#110283)

Some assertions with floating-point values are failing on serverless 
because we run tests with three shards with serverless. This can cause
variations in precision because data may arrive in different orders. For
example, sum([a, b, c]) can yield a different precision than sum([a, c,
b]). This change introduces tolerance for precision differences beyond
e-10, which should be acceptable for ESQL.

Author: dnhatn

x-pack/plugin/esql/qa/server/mixed-cluster/src/javaRestTest/java/org/elasticsearch/xpack/esql/qa/mixed/MixedClusterEsqlSpecIT.java

@@ -73,4 +73,9 @@ protected void shouldSkipTest(String testName) throws IOException {
     protected boolean supportsAsync() {
         return oldClusterHasFeature(ASYNC_QUERY_FEATURE_ID);
     }
+
+    @Override
+    protected boolean enableRoundingDoubleValuesOnAsserting() {
+        return true;
+    }
 }

x-pack/plugin/esql/qa/server/multi-clusters/src/javaRestTest/java/org/elasticsearch/xpack/esql/ccq/MultiClusterSpecIT.java

@@ -231,4 +231,9 @@ static boolean hasIndexMetadata(String query) {
         }
         return false;
     }
+
+    @Override
+    protected boolean enableRoundingDoubleValuesOnAsserting() {
+        return true;
+    }
 }

x-pack/plugin/esql/qa/server/multi-node/src/javaRestTest/java/org/elasticsearch/xpack/esql/qa/multi_node/EsqlSpecIT.java

@@ -24,4 +24,9 @@ protected String getTestRestCluster() {
     public EsqlSpecIT(String fileName, String groupName, String testName, Integer lineNumber, CsvTestCase testCase, Mode mode) {
         super(fileName, groupName, testName, lineNumber, testCase, mode);
     }
+
+    @Override
+    protected boolean enableRoundingDoubleValuesOnAsserting() {
+        return true;
+    }
 }

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

@@ -30,6 +30,9 @@
 import org.junit.Before;
 
 import java.io.IOException;
+import java.math.BigDecimal;
+import java.math.MathContext;
+import java.math.RoundingMode;
 import java.net.URL;
 import java.util.ArrayList;
 import java.util.List;
@@ -187,10 +190,10 @@ protected void assertResults(
         Logger logger
     ) {
         assertMetadata(expected, actualColumns, logger);
-        assertData(expected, actualValues, testCase.ignoreOrder, logger, EsqlSpecTestCase::valueMapper);
+        assertData(expected, actualValues, testCase.ignoreOrder, logger, this::valueMapper);
     }
 
-    private static Object valueMapper(CsvTestUtils.Type type, Object value) {
+    private Object valueMapper(CsvTestUtils.Type type, Object value) {
         if (value == null) {
             return "null";
         }
@@ -205,9 +208,30 @@ private static Object valueMapper(CsvTestUtils.Type type, Object value) {
                 } catch (Throwable ignored) {}
             }
         }
+        if (type == CsvTestUtils.Type.DOUBLE && enableRoundingDoubleValuesOnAsserting()) {
+            if (value instanceof List<?> vs) {
+                List<Object> values = new ArrayList<>();
+                for (Object v : vs) {
+                    values.add(valueMapper(type, v));
+                }
+                return values;
+            } else if (value instanceof Double d) {
+                return new BigDecimal(d).round(new MathContext(10, RoundingMode.DOWN)).doubleValue();
+            } else if (value instanceof String s) {
+                return new BigDecimal(s).round(new MathContext(10, RoundingMode.DOWN)).doubleValue();
+            }
+        }
         return value.toString();
     }
 
+    /**
+     * Rounds double values when asserting double values returned in queries.
+     * By default, no rounding is performed.
+     */
+    protected boolean enableRoundingDoubleValuesOnAsserting() {
+        return false;
+    }
+
     private static String normalizedPoint(CsvTestUtils.Type type, double x, double y) {
         if (type == CsvTestUtils.Type.GEO_POINT) {
             return normalizedGeoPoint(x, y);