feat: support keyword "only" for postgresql (#1952)

Co-authored-by: mjh <[email protected]>

Author: SheldonKubor

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

@@ -65,6 +65,8 @@ public class PlainSelect extends Select {
      */
     private boolean isUsingFinal = false;
 
+    private boolean isUsingOnly = false;
+
     @Deprecated
     public boolean isUseBrackets() {
         return false;
@@ -213,6 +215,19 @@ public PlainSelect withUsingFinal(boolean usingFinal) {
         return this;
     }
 
+    public boolean isUsingOnly() {
+        return isUsingOnly;
+    }
+
+    public void setUsingOnly(boolean usingOnly) {
+        isUsingOnly = usingOnly;
+    }
+
+    public PlainSelect withUsingOnly(boolean usingOnly) {
+        this.setUsingOnly(usingOnly);
+        return this;
+    }
+
     @Override
     public void accept(SelectVisitor selectVisitor) {
         selectVisitor.visit(this);
@@ -439,7 +454,11 @@ public StringBuilder appendSelectBodyTo(StringBuilder builder) {
         }
 
         if (fromItem != null) {
-            builder.append(" FROM ").append(fromItem);
+            builder.append(" FROM ");
+            if (isUsingOnly) {
+                builder.append("ONLY ");
+            }
+            builder.append(fromItem);
             if (lateralViews != null) {
                 for (LateralView lateralView : lateralViews) {
                     builder.append(" ").append(lateralView);

src/main/java/net/sf/jsqlparser/util/deparser/SelectDeParser.java

@@ -210,6 +210,9 @@ public void visit(PlainSelect plainSelect) {
 
         if (plainSelect.getFromItem() != null) {
             buffer.append(" FROM ");
+            if (plainSelect.isUsingOnly()) {
+                buffer.append("ONLY ");
+            }
             plainSelect.getFromItem().accept(this);
 
             if (plainSelect.getFromItem() instanceof Table) {

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

@@ -2277,6 +2277,10 @@ PlainSelect PlainSelect() #PlainSelect:
         [ lateralViews=LateralViews() ]
         [ LOOKAHEAD(2) joins=JoinsList() ]
     ]
+    [ LOOKAHEAD(3) <K_FROM> <K_ONLY> { plainSelect.setUsingOnly(true); } fromItem=FromItem()
+            [ lateralViews=LateralViews() ]
+            [ LOOKAHEAD(2) joins=JoinsList() ]
+    ]
 
     // Clickhouse FINAL as shown at https://clickhouse.com/docs/en/operations/settings/settings#final
     [ LOOKAHEAD(2) <K_FINAL> { plainSelect.setUsingFinal(true); } ]

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

@@ -5806,4 +5806,11 @@ public void testIssue1907() throws JSQLParserException {
                 "SELECT * FROM (SELECT year, person, SUM(amount) FROM rentals GROUP BY year, person) t1 ORDER BY year DESC WITH ROLLUP";
         assertSqlCanBeParsedAndDeparsed(stmt2);
     }
+
+    @Test
+    public void testIssue1908() throws JSQLParserException {
+        // postgresql14
+        String stmt = "SELECT * FROM ONLY sys_business_rule";
+        assertSqlCanBeParsedAndDeparsed(stmt);
+    }
 }