fixes #1013 - refactored fromitem grammar to drastically improve performance

Author: wumpz

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

@@ -1935,6 +1935,7 @@ List<Table> IntoClause():
 FromItem FromItem():
 {
     FromItem fromItem = null;
+    FromItem fromItem2 = null;
     Pivot pivot = null;
     UnPivot unpivot = null;
     Alias alias = null;
@@ -1950,14 +1951,13 @@ FromItem FromItem():
                 (
                     "("
                         (
-                        LOOKAHEAD(SubJoin())
-                        fromItem=SubJoin()
-                        |
-                        LOOKAHEAD(3)
+                        LOOKAHEAD(3) fromItem2=FromItem()
+                          { fromItem = new ParenthesisFromItem(fromItem2); }
+                        [ fromItem = SubJoin(fromItem2) ]
+                        /* LOOKAHEAD(SubJoin())
+                        fromItem=SubJoin() */
+                        | 
                         fromItem=SubSelect()
-                        |
-                        fromItem=FromItem()
-                          { fromItem = new ParenthesisFromItem(fromItem); }
                         )
                     ")"
                     [ LOOKAHEAD(2) unpivot=UnPivot() { fromItem.setUnPivot(unpivot); } ]
@@ -2049,19 +2049,17 @@ LateralSubSelect LateralSubSelect():
     }
 }
 
-FromItem SubJoin():
+FromItem SubJoin(FromItem fromItem):
 {
-    FromItem fromItem = null;
     Join join = null;
     List<Join> joinList = null;
 }
 {
-    fromItem=FromItem()
-	joinList=SubJoinsList()
+    joinList=SubJoinsList()
     {
-		SubJoin subJoin = new SubJoin();
-		subJoin.setLeft(fromItem);
-		subJoin.setJoinList(joinList);
+        SubJoin subJoin = new SubJoin();
+        subJoin.setLeft(fromItem);
+        subJoin.setJoinList(joinList);
         return subJoin;
     }
 }

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

@@ -9,6 +9,7 @@
  */
 package net.sf.jsqlparser.statement.select;
 
+import java.util.logging.Logger;
 import static net.sf.jsqlparser.test.TestUtils.assertSqlCanBeParsedAndDeparsed;
 import org.junit.Ignore;
 import org.junit.Test;
@@ -48,29 +49,57 @@ public void testIssue856() throws JSQLParserException {
         String sql = "SELECT " + buildRecursiveBracketExpression("if(month(today()) = 3, sum(\"Table5\".\"Month 002\"), $1)", "0", 5) + " FROM mytbl";
         assertSqlCanBeParsedAndDeparsed(sql);
     }
-    
+
     @Test
     public void testRecursiveBracketExpressionIssue1019() {
         assertEquals("IF(1=1, 1, 2)", buildRecursiveBracketExpression("IF(1=1, $1, 2)", "1", 0));
         assertEquals("IF(1=1, IF(1=1, 1, 2), 2)", buildRecursiveBracketExpression("IF(1=1, $1, 2)", "1", 1));
         assertEquals("IF(1=1, IF(1=1, IF(1=1, 1, 2), 2), 2)", buildRecursiveBracketExpression("IF(1=1, $1, 2)", "1", 2));
     }
-    
+
     @Test
     public void testRecursiveBracketExpressionIssue1019_2() throws JSQLParserException {
         doIncreaseOfParseTimeTesting("IF(1=1, $1, 2)", "1", 10);
     }
 
+    @Test
+    public void testIssue1013() throws JSQLParserException {
+        assertSqlCanBeParsedAndDeparsed("SELECT ((((((((((((((((tblA)))))))))))))))) FROM mytable");
+    }
+
+    @Test
+    public void testIssue1013_2() throws JSQLParserException {
+        assertSqlCanBeParsedAndDeparsed("SELECT * FROM ((((((((((((((((tblA))))))))))))))))");
+    }
+
+    @Test
+    public void testIssue1013_3() throws JSQLParserException {
+        assertSqlCanBeParsedAndDeparsed("SELECT * FROM (((tblA)))");
+    }
+
+    @Test
+    public void testIssue1013_4() throws JSQLParserException {
+        String s = "tblA";
+        for (int i = 1; i < 100; i++) {
+            s = "(" + s + ")";
+        }
+        String sql = "SELECT * FROM " + s;
+        LOG.info("testing " + sql);
+        assertSqlCanBeParsedAndDeparsed(sql);
+    }
+    private static final Logger LOG = Logger.getLogger(NestedBracketsPerformanceTest.class.getName());
+
     /**
-     * Try to avoid or border exceptionally big parsing time increments by adding more bracket constructs.
+     * Try to avoid or border exceptionally big parsing time increments by
+     * adding more bracket constructs.
      *
      * @throws JSQLParserException
      */
     @Test
     public void testIncreaseOfParseTime() throws JSQLParserException {
         doIncreaseOfParseTimeTesting("concat($1,'B')", "'A'", 20);
     }
-    
+
     private void doIncreaseOfParseTimeTesting(String template, String finalExpression, int maxDepth) throws JSQLParserException {
         long oldDurationTime = 1000;
         int countProblematic = 0;
@@ -100,7 +129,7 @@ public void testRecursiveBracketExpression() {
         assertEquals("concat(concat('A','B'),'B')", buildRecursiveBracketExpression("concat($1,'B')", "'A'", 1));
         assertEquals("concat(concat(concat('A','B'),'B'),'B')", buildRecursiveBracketExpression("concat($1,'B')", "'A'", 2));
     }
-    
+
     private String buildRecursiveBracketExpression(String template, String finalExpression, int depth) {
         if (depth == 0) {
             return template.replace("$1", finalExpression);