Retrofit Like to be foldable but LikePattern not

Original commit: elastic/x-pack-elasticsearch@0438482def

sql/server/src/main/java/org/elasticsearch/xpack/sql/expression/regex/Like.java

@@ -24,9 +24,14 @@ public class Like extends BinaryExpression {
         return (LikePattern) super.right();
     }
 
+    @Override
+    public boolean foldable() {
+        return left().foldable();
+    }
+
     @Override
     public Object fold() {
-        Pattern p = Pattern.compile(right().fold().toString());
+        Pattern p = Pattern.compile(right().asJavaRegex());
         return p.matcher(left().fold().toString()).matches();
     }
 

sql/server/src/main/java/org/elasticsearch/xpack/sql/expression/regex/LikePattern.java

@@ -69,17 +69,6 @@ public class LikePattern extends LeafExpression {
         return indexNameWildcard;
     }
 
-    @Override
-    public boolean foldable() {
-        return false;
-    }
-
-    @Override
-    public Object fold() {
-        // being in Java, the Java regex is returned
-        return asJavaRegex();
-    }
-
     @Override
     public boolean nullable() {
         return false;

sql/server/src/test/java/org/elasticsearch/xpack/sql/optimizer/OptimizerTests.java

@@ -26,6 +26,9 @@ import org.elasticsearch.xpack.sql.expression.predicate.LessThanOrEqual;
 import org.elasticsearch.xpack.sql.expression.predicate.Not;
 import org.elasticsearch.xpack.sql.expression.predicate.Or;
 import org.elasticsearch.xpack.sql.expression.predicate.Range;
+import org.elasticsearch.xpack.sql.expression.regex.Like;
+import org.elasticsearch.xpack.sql.expression.regex.LikePattern;
+import org.elasticsearch.xpack.sql.expression.regex.RLike;
 import org.elasticsearch.xpack.sql.optimizer.Optimizer.BinaryComparisonSimplification;
 import org.elasticsearch.xpack.sql.optimizer.Optimizer.BooleanLiteralsOnTheRight;
 import org.elasticsearch.xpack.sql.optimizer.Optimizer.BooleanSimplification;
@@ -236,6 +239,13 @@ public class OptimizerTests extends ESTestCase {
         assertEquals(Literal.TRUE, new ConstantFolding().rule(new Not(EMPTY, Literal.FALSE)));
     }
 
+    public void testConstantFoldingLikes() {
+        assertEquals(Literal.TRUE,
+                new ConstantFolding().rule(new Like(EMPTY, Literal.of(EMPTY, "test_emp"), new LikePattern(EMPTY, "test%", (char) 0))));
+        assertEquals(Literal.TRUE,
+                new ConstantFolding().rule(new RLike(EMPTY, Literal.of(EMPTY, "test_emp"), Literal.of(EMPTY, "test.emp"))));
+    }
+
     public void testBinaryComparisonSimplification() {
         assertEquals(Literal.TRUE, new BinaryComparisonSimplification().rule(new Equals(EMPTY, L(5), L(5))));
         assertEquals(Literal.TRUE, new BinaryComparisonSimplification().rule(new GreaterThanOrEqual(EMPTY, L(5), L(5))));