remove to json string

Signed-off-by: xinyual <xinyual@amazon.com>

Author: xinyual

core/src/main/java/org/opensearch/sql/expression/function/PPLBuiltinOperators.java

@@ -34,7 +34,6 @@
 import org.opensearch.sql.expression.function.jsonUDF.JsonFunctionImpl;
 import org.opensearch.sql.expression.function.jsonUDF.JsonKeysFunctionImpl;
 import org.opensearch.sql.expression.function.jsonUDF.JsonSetFunctionImpl;
-import org.opensearch.sql.expression.function.jsonUDF.ToJsonStringFunctionImpl;
 import org.opensearch.sql.expression.function.udf.CryptographicFunction;
 import org.opensearch.sql.expression.function.udf.datetime.AddSubDateFunction;
 import org.opensearch.sql.expression.function.udf.datetime.CurrentFunction;
@@ -68,8 +67,6 @@ public class PPLBuiltinOperators extends ReflectiveSqlOperatorTable {
   // Math functions
   public static final SqlOperator SPAN = new SpanFunctionImpl().toUDF("SPAN");
   public static final SqlOperator JSON = new JsonFunctionImpl().toUDF("JSON");
-  public static final SqlOperator TO_JSON_STRING =
-      new ToJsonStringFunctionImpl().toUDF("TO_JSON_STRING");
   public static final SqlOperator JSON_ARRAY_LENGTH =
       new JsonArrayLengthFunctionImpl().toUDF("JSON_ARRAY_LENGTH");
   public static final SqlOperator JSON_EXTRACT =

core/src/main/java/org/opensearch/sql/expression/function/PPLFuncImpTable.java

@@ -319,7 +319,6 @@ void populate() {
                   Stream.concat(Stream.of(builder.makeFlag(NULL_ON_NULL)), Arrays.stream(args))
                       .toArray(RexNode[]::new))));
       registerOperator(JSON, PPLBuiltinOperators.JSON);
-      registerOperator(TO_JSON_STRING, PPLBuiltinOperators.TO_JSON_STRING);
       registerOperator(JSON_ARRAY_LENGTH, PPLBuiltinOperators.JSON_ARRAY_LENGTH);
       registerOperator(JSON_EXTRACT, PPLBuiltinOperators.JSON_EXTRACT);
       registerOperator(JSON_KEYS, PPLBuiltinOperators.JSON_KEYS);

core/src/main/java/org/opensearch/sql/expression/function/jsonUDF/ToJsonStringFunctionImpl.java

@@ -448,8 +448,8 @@ integTest {
 
     dependsOn ':opensearch-sql-plugin:bundlePlugin'
     if(getOSFamilyType() != "windows") {
-        dependsOn startPrometheus
-        finalizedBy stopPrometheus
+        //dependsOn startPrometheus
+        //finalizedBy stopPrometheus
     }
 
     // enable calcite codegen in IT

integ-test/build.gradle

@@ -85,20 +85,6 @@ public void testJsonArrayWithDifferentType() {
     verifyDataRows(actual, rows("[1,\"123\",\"{\\\"name\\\":3}\"]"));
   }
 
-  @Test
-  public void testToJsonString() {
-    JSONObject actual =
-        executeQuery(
-            String.format(
-                "source=%s |  eval a = to_json_string(name) | fields a" + " | head 1",
-                TEST_INDEX_GAME_OF_THRONES));
-
-    verifySchema(actual, schema("a", "string"));
-
-    verifyDataRows(
-        actual, rows("{\"firstname\":\"Daenerys\",\"lastname\":\"Targaryen\",\"ofHerName\":1}"));
-  }
-
   @Test
   public void testJsonArrayLength() {
     JSONObject actual =

integ-test/src/test/java/org/opensearch/sql/calcite/standalone/CalcitePPLJsonBuiltinFunctionIT.java

@@ -372,7 +372,6 @@ JSON_VALID:                         'JSON_VALID';
 JSON:                               'JSON';
 JSON_OBJECT:                        'JSON_OBJECT';
 JSON_ARRAY:                         'JSON_ARRAY';
-TO_JSON_STRING:                     'TO_JSON_STRING';
 JSON_ARRAY_LENGTH:                  'JSON_ARRAY_LENGTH';
 JSON_EXTRACT:                       'JSON_EXTRACT';
 JSON_KEYS:                          'JSON_KEYS';

ppl/src/main/antlr/OpenSearchPPLLexer.g4

@@ -702,7 +702,6 @@ jsonFunctionName
    : JSON
    | JSON_OBJECT
    | JSON_ARRAY
-   | TO_JSON_STRING
    | JSON_ARRAY_LENGTH
    | JSON_EXTRACT
    | JSON_KEYS