Add isnotempty PPL function

Adds `isnotempty(field)` function to PPL that returns true when a field
is not null and not an empty string — the logical negation of
`isempty(field)`.

Implementation: NOT(IS_NULL(arg) OR IS_EMPTY(arg))

- ANTLR grammar: added ISNOTEMPTY token and parser rules in all three
  grammar modules (ppl, language-grammar, async-query-core)
- BuiltinFunctionName: added IS_NOT_EMPTY enum constant
- PPLFuncImpTable: registered Calcite implementation
- Integration test: testIsNotEmpty in CalcitePPLConditionBuiltinFunctionIT
- Documentation: added ISNOTEMPTY section to condition functions docs

Resolves #5182

Signed-off-by: Luca Cavenaghi <lucacavenaghics97@gmail.com>

Author: lucacavenaghi97

async-query-core/src/main/antlr/OpenSearchPPLLexer.g4

@@ -373,6 +373,7 @@ REPLACE:                            'REPLACE';
 REVERSE:                            'REVERSE';
 CAST:                               'CAST';
 ISEMPTY:                            'ISEMPTY';
+ISNOTEMPTY:                         'ISNOTEMPTY';
 ISBLANK:                            'ISBLANK';
 
 // JSON TEXT FUNCTIONS

async-query-core/src/main/antlr/OpenSearchPPLParser.g4

@@ -468,6 +468,7 @@ positionFunction
 booleanExpression
    : booleanFunctionCall                                                # booleanFunctionCallExpr
    | isEmptyExpression                                                  # isEmptyExpr
+   | isNotEmptyExpression                                               # isNotEmptyExpr
    | valueExpressionList NOT? IN LT_SQR_PRTHS subSearch RT_SQR_PRTHS    # inSubqueryExpr
    | EXISTS LT_SQR_PRTHS subSearch RT_SQR_PRTHS                         # existsSubqueryExpr
    | cidrMatchFunctionCall                                              # cidrFunctionCallExpr
@@ -477,6 +478,10 @@ booleanExpression
    : (ISEMPTY | ISBLANK) LT_PRTHS functionArg RT_PRTHS
    ;
 
+ isNotEmptyExpression
+   : ISNOTEMPTY LT_PRTHS functionArg RT_PRTHS
+   ;
+
  caseFunction
     : CASE LT_PRTHS logicalExpression COMMA valueExpression (COMMA logicalExpression COMMA valueExpression)* (ELSE valueExpression)? RT_PRTHS
     ;
@@ -860,6 +865,7 @@ textFunctionName
    | REPLACE
    | REVERSE
    | ISEMPTY
+   | ISNOTEMPTY
    | ISBLANK
    ;
 

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

@@ -289,6 +289,7 @@ public enum BuiltinFunctionName {
 
   IS_PRESENT(FunctionName.of("ispresent")),
   IS_EMPTY(FunctionName.of("isempty")),
+  IS_NOT_EMPTY(FunctionName.of("isnotempty")),
   IS_BLANK(FunctionName.of("isblank")),
 
   ROW_NUMBER(FunctionName.of("row_number")),

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

@@ -91,6 +91,7 @@
 import static org.opensearch.sql.expression.function.BuiltinFunctionName.INTERNAL_TRANSLATE3;
 import static org.opensearch.sql.expression.function.BuiltinFunctionName.IS_BLANK;
 import static org.opensearch.sql.expression.function.BuiltinFunctionName.IS_EMPTY;
+import static org.opensearch.sql.expression.function.BuiltinFunctionName.IS_NOT_EMPTY;
 import static org.opensearch.sql.expression.function.BuiltinFunctionName.IS_NOT_NULL;
 import static org.opensearch.sql.expression.function.BuiltinFunctionName.IS_NULL;
 import static org.opensearch.sql.expression.function.BuiltinFunctionName.IS_PRESENT;
@@ -1252,6 +1253,17 @@ void populate() {
                       builder.makeCall(SqlStdOperatorTable.IS_NULL, arg),
                       builder.makeCall(SqlStdOperatorTable.IS_EMPTY, arg)),
           PPLTypeChecker.family(SqlTypeFamily.ANY));
+      register(
+          IS_NOT_EMPTY,
+          (FunctionImp1)
+              (builder, arg) ->
+                  builder.makeCall(
+                      SqlStdOperatorTable.NOT,
+                      builder.makeCall(
+                          SqlStdOperatorTable.OR,
+                          builder.makeCall(SqlStdOperatorTable.IS_NULL, arg),
+                          builder.makeCall(SqlStdOperatorTable.IS_EMPTY, arg))),
+          PPLTypeChecker.family(SqlTypeFamily.ANY));
       register(
           IS_BLANK,
           (FunctionImp1)

docs/user/ppl/functions/condition.md

@@ -642,8 +642,40 @@ fetched rows / total rows = 4/4
 | False         |         | True              | null     |
 +---------------+---------+-------------------+----------+
 ```
-  
-## EARLIEST  
+
+## ISNOTEMPTY
+
+### Description
+
+Usage: `isnotempty(field)` returns true if the field is not null and is not an empty string.
+
+**Argument type:** All supported data types.
+**Return type:** `BOOLEAN`
+
+### Example
+
+```ppl
+source=accounts
+| eval temp = ifnull(employer, '   ')
+| eval `isnotempty(employer)` = isnotempty(employer), `isnotempty(temp)` = isnotempty(temp)
+| fields `isnotempty(temp)`, temp, `isnotempty(employer)`, employer
+```
+
+Expected output:
+
+```text
+fetched rows / total rows = 4/4
++------------------+---------+----------------------+----------+
+| isnotempty(temp) | temp    | isnotempty(employer) | employer |
+|------------------+---------+----------------------+----------|
+| True             | Pyrami  | True                 | Pyrami   |
+| True             | Netagy  | True                 | Netagy   |
+| True             | Quility | True                 | Quility  |
+| True             |         | False                | null     |
++------------------+---------+----------------------+----------|
+```
+
+## EARLIEST
 
 ### Description  
 

docs/user/ppl/functions/index.md

@@ -54,6 +54,7 @@ PPL supports a wide range of built-in functions for data processing and analysis
   - [ISPRESENT](condition.md/#ispresent)
   - [ISBLANK](condition.md/#isblank)
   - [ISEMPTY](condition.md/#isempty)
+  - [ISNOTEMPTY](condition.md/#isnotempty)
   - [EARLIEST](condition.md/#earliest)
   - [LATEST](condition.md/#latest)
   - [REGEXP_MATCH](condition.md/#regexp_match)

integ-test/src/test/java/org/opensearch/sql/calcite/remote/CalcitePPLConditionBuiltinFunctionIT.java

@@ -282,6 +282,28 @@ public void testIsEmpty() throws IOException {
     verifyDataRows(actual, rows(null, 10), rows("", 57));
   }
 
+  @Test
+  public void testIsNotEmpty() throws IOException {
+    JSONObject actual =
+        executeQuery(
+            String.format(
+                "source=%s | where isnotempty(name) | fields name, age",
+                TEST_INDEX_STATE_COUNTRY_WITH_NULL));
+
+    verifySchema(actual, schema("name", "string"), schema("age", "int"));
+
+    // isnotempty = NOT isempty. isempty returns (null,10) and ("",57).
+    // So isnotempty returns everything else: Jake, Hello, John, Jane, Kevin, whitespace.
+    verifyDataRows(
+        actual,
+        rows("Jake", 70),
+        rows("Hello", 30),
+        rows("John", 25),
+        rows("Jane", 20),
+        rows("Kevin", null),
+        rows("    ", 27));
+  }
+
   @Test
   public void testIsBlank() throws IOException {
     JSONObject actual =

language-grammar/src/main/antlr4/OpenSearchPPLLexer.g4

@@ -419,6 +419,7 @@ BETWEEN:                            'BETWEEN';
 CIDRMATCH:                          'CIDRMATCH';
 ISPRESENT:                          'ISPRESENT';
 ISEMPTY:                            'ISEMPTY';
+ISNOTEMPTY:                         'ISNOTEMPTY';
 ISBLANK:                            'ISBLANK';
 
 // FLOWCONTROL FUNCTIONS

language-grammar/src/main/antlr4/OpenSearchPPLParser.g4

@@ -851,6 +851,7 @@ conditionFunctionBase
    | EARLIEST
    | LATEST
    | ISEMPTY
+   | ISNOTEMPTY
    | ISBLANK
    ;
 
@@ -877,6 +878,7 @@ textFunctionName
    | REPLACE
    | REVERSE
    | ISEMPTY
+   | ISNOTEMPTY
    | ISBLANK
    ;
 

ppl/src/main/antlr/OpenSearchPPLLexer.g4

@@ -463,6 +463,7 @@ CIDRMATCH:                          'CIDRMATCH';
 BETWEEN:                            'BETWEEN';
 ISPRESENT:                          'ISPRESENT';
 ISEMPTY:                            'ISEMPTY';
+ISNOTEMPTY:                         'ISNOTEMPTY';
 ISBLANK:                            'ISBLANK';
 
 // COLLECTION FUNCTIONS