feat: allow GROUP BY ALL and DISTINCT modifiers for PostgreSQL

Resolves #2785

Author: princejain756

src/main/java/net/sf/jsqlparser/statement/select/GroupByElement.java

@@ -33,6 +33,8 @@ public enum SortDirection {
     private List<ExpressionList<Expression>> groupingSets = new ArrayList<>();
     // postgres rollup is an ExpressionList
     private boolean mysqlWithRollup = false;
+    private boolean all = false;
+    private boolean distinct = false;
 
     public boolean isUsingBrackets() {
         return groupByExpressions.isUsingBrackets();
@@ -115,6 +117,12 @@ public String toString() {
     public void appendTo(StringBuilder builder, Consumer<ExpressionList<?>> listRenderer,
             Consumer<Expression> expressionRenderer) {
         builder.append("GROUP BY ");
+        if (all) {
+            builder.append("ALL ");
+        }
+        if (distinct) {
+            builder.append("DISTINCT ");
+        }
         if (groupByExpressions != null) {
             if (hasGroupBySortDirections()) {
                 appendOrderedExpressions(builder, expressionRenderer);
@@ -200,4 +208,22 @@ public GroupByElement setMysqlWithRollup(boolean mysqlWithRollup) {
         this.mysqlWithRollup = mysqlWithRollup;
         return this;
     }
+
+    public boolean isAll() {
+        return all;
+    }
+
+    public GroupByElement setAll(boolean all) {
+        this.all = all;
+        return this;
+    }
+
+    public boolean isDistinct() {
+        return distinct;
+    }
+
+    public GroupByElement setDistinct(boolean distinct) {
+        this.distinct = distinct;
+        return this;
+    }
 }

src/main/jjtree/net/sf/jsqlparser/parser/JSqlParserCC.jjt

@@ -11031,6 +11031,11 @@ GroupByElement GroupByColumnReferences():
 }
 {
     <K_GROUP> <K_BY>
+    // PostgreSQL: GROUP BY [ ALL | DISTINCT ] grouping_element [, ...]
+    [ LOOKAHEAD({ Dialect.POSTGRESQL.name().equals(getAsString(Feature.dialect))
+            && (getToken(1).kind == K_ALL || getToken(1).kind == K_DISTINCT) })
+        ( <K_ALL> { groupBy.setAll(true); } | <K_DISTINCT> { groupBy.setDistinct(true); } )
+    ]
     (
         LOOKAHEAD(2) (
             <K_GROUPING> <K_SETS>

src/test/java/net/sf/jsqlparser/statement/select/SelectTest.java

@@ -2398,6 +2398,20 @@ public void testBooleanTestAfterPredicate() throws JSQLParserException {
         assertSqlCanBeParsedAndDeparsed("SELECT * FROM t WHERE a IS TRUE IS FALSE");
     }
 
+    @Test
+    public void testGroupByAllDistinct_PostgreSql() throws JSQLParserException {
+        // PostgreSQL: GROUP BY [ ALL | DISTINCT ] grouping_element [, ...]
+        assertSqlCanBeParsedAndDeparsed(
+                "SELECT 1 GROUP BY DISTINCT GROUPING SETS ((1), (1))",
+                false, parser -> parser.withDialect(Dialect.POSTGRESQL));
+        assertSqlCanBeParsedAndDeparsed(
+                "SELECT 1 GROUP BY ALL GROUPING SETS ((1), (2))",
+                false, parser -> parser.withDialect(Dialect.POSTGRESQL));
+        assertSqlCanBeParsedAndDeparsed(
+                "SELECT a FROM t GROUP BY DISTINCT a",
+                false, parser -> parser.withDialect(Dialect.POSTGRESQL));
+    }
+
     @Test
     public void testIsUnknown() throws JSQLParserException {
         String statement = "SELECT col FROM tbl WHERE col IS UNKNOWN";