Remove optional seed from ES|QL SAMPLE (#128887)

* Remove optional seed from ES|QL SAMPLE

* make it clear that seed is for testing

Author: jan-elastic

x-pack/plugin/esql/compute/src/main/java/org/elasticsearch/compute/operator/SampleOperator.java

@@ -9,6 +9,7 @@
 
 import org.elasticsearch.TransportVersion;
 import org.elasticsearch.TransportVersions;
+import org.elasticsearch.common.Randomness;
 import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.io.stream.NamedWriteableRegistry;
 import org.elasticsearch.common.io.stream.StreamInput;
@@ -27,16 +28,29 @@
 
 public class SampleOperator implements Operator {
 
-    public record Factory(double probability, int seed) implements OperatorFactory {
+    public static class Factory implements OperatorFactory {
+
+        private final double probability;
+        private final Integer seed;
+
+        public Factory(double probability) {
+            this(probability, null);
+        }
+
+        // visible for testing
+        Factory(double probability, Integer seed) {
+            this.probability = probability;
+            this.seed = seed;
+        }
 
         @Override
         public SampleOperator get(DriverContext driverContext) {
-            return new SampleOperator(probability, seed);
+            return new SampleOperator(probability, seed == null ? Randomness.get().nextInt() : seed);
         }
 
         @Override
         public String describe() {
-            return "SampleOperator[probability = " + probability + ", seed = " + seed + "]";
+            return "SampleOperator[probability = " + probability + "]";
         }
     }
 

x-pack/plugin/esql/compute/src/test/java/org/elasticsearch/compute/operator/SampleOperatorTests.java

@@ -21,7 +21,6 @@
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.greaterThan;
 import static org.hamcrest.Matchers.lessThan;
-import static org.hamcrest.Matchers.matchesPattern;
 
 public class SampleOperatorTests extends OperatorTestCase {
 
@@ -46,7 +45,7 @@ protected SampleOperator.Factory simple(SimpleOptions options) {
 
     @Override
     protected Matcher<String> expectedDescriptionOfSimple() {
-        return matchesPattern("SampleOperator\\[probability = 0.5, seed = -?\\d+]");
+        return equalTo("SampleOperator[probability = 0.5]");
     }
 
     @Override

x-pack/plugin/esql/src/main/antlr/EsqlBaseParser.g4

@@ -312,5 +312,5 @@ completionCommand
     ;
 
 sampleCommand
-    : DEV_SAMPLE probability=decimalValue seed=integerValue?
+    : DEV_SAMPLE probability=decimalValue
     ;

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

@@ -62,8 +62,7 @@ protected LogicalPlan rule(Sample sample, LogicalOptimizerContext context) {
         var child = sample.child();
         if (child instanceof Sample sampleChild) {
             var probability = combinedProbability(context, sample, sampleChild);
-            var seed = combinedSeed(context, sample, sampleChild);
-            plan = new Sample(sample.source(), probability, seed, sampleChild.child());
+            plan = new Sample(sample.source(), probability, sampleChild.child());
         } else if (child instanceof Enrich
             || child instanceof Eval
             || child instanceof Filter
@@ -82,22 +81,4 @@ private static Expression combinedProbability(LogicalOptimizerContext context, S
         var childProbability = (double) Foldables.valueOf(context.foldCtx(), child.probability());
         return Literal.of(parent.probability(), parentProbability * childProbability);
     }
-
-    private static Expression combinedSeed(LogicalOptimizerContext context, Sample parent, Sample child) {
-        var parentSeed = parent.seed();
-        var childSeed = child.seed();
-        Expression seed;
-        if (parentSeed != null) {
-            if (childSeed != null) {
-                var seedValue = (int) Foldables.valueOf(context.foldCtx(), parentSeed);
-                seedValue ^= (int) Foldables.valueOf(context.foldCtx(), childSeed);
-                seed = Literal.of(parentSeed, seedValue);
-            } else {
-                seed = parentSeed;
-            }
-        } else {
-            seed = childSeed;
-        }
-        return seed;
-    }
 }

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/optimizer/rules/physical/local/PushSampleToSource.java

@@ -33,9 +33,6 @@ protected PhysicalPlan rule(SampleExec sample, LocalPhysicalOptimizerContext ctx
             }
 
             var sampleQuery = new RandomSamplingQueryBuilder((double) Foldables.valueOf(ctx.foldCtx(), sample.probability()));
-            if (sample.seed() != null) {
-                sampleQuery.seed((int) Foldables.valueOf(ctx.foldCtx(), sample.seed()));
-            }
 
             fullQuery.filter(sampleQuery);