refactor: TableFunction extends Function, supports LATERAL prefix

- implements `Function`, extends `FromItem`
- supports `LATERAL` prefix
- fixes #1835

Signed-off-by: Andreas Reichel <andreas@manticore-projects.com>

Author: manticore-projects

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

@@ -13,31 +13,59 @@
 import net.sf.jsqlparser.expression.Function;
 
 @SuppressWarnings({"PMD.UncommentedEmptyMethodBody"})
-public class TableFunction extends SelectItem<Function> implements FromItem {
+public class TableFunction extends Function implements FromItem {
+    private String prefix = null;
+    private Alias alias = null;
+    private Pivot pivot = null;
+    private UnPivot unPivot = null;
+    private Function function;
 
-    @Override
-    public void accept(FromItemVisitor fromItemVisitor) {
-        fromItemVisitor.visit(this);
+    public TableFunction(Function function) {
+        this.function = function;
     }
 
-    @Override
-    public Pivot getPivot() {
-        return null;
+    public TableFunction(String prefix, Function function) {
+        this.prefix = prefix;
+        this.function = function;
     }
 
-    @Override
-    public void setPivot(Pivot pivot) {
+    public Function getFunction() {
+        return function;
+    }
 
+    @Deprecated
+    public Function getExpression() {
+        return getFunction();
+    }
+
+
+    public TableFunction setFunction(Function function) {
+        this.function = function;
+        return this;
+    }
+
+    public String getPrefix() {
+        return prefix;
+    }
+
+    public TableFunction setPrefix(String prefix) {
+        this.prefix = prefix;
+        return this;
     }
 
     @Override
-    public UnPivot getUnPivot() {
-        return null;
+    public void accept(FromItemVisitor fromItemVisitor) {
+        fromItemVisitor.visit(this);
     }
 
     @Override
-    public void setUnPivot(UnPivot unpivot) {
+    public Alias getAlias() {
+        return alias;
+    }
 
+    @Override
+    public void setAlias(Alias alias) {
+        this.alias = alias;
     }
 
     @Override
@@ -46,18 +74,49 @@ public TableFunction withAlias(Alias alias) {
     }
 
     @Override
-    public TableFunction withExpression(Function function) {
-        return (TableFunction) super.withExpression(function);
+    public Pivot getPivot() {
+        return pivot;
+    }
+
+    @Override
+    public void setPivot(Pivot pivot) {
+        this.pivot = pivot;
     }
 
     @Override
     public TableFunction withPivot(Pivot pivot) {
         return (TableFunction) FromItem.super.withPivot(pivot);
     }
 
+    @Override
+    public UnPivot getUnPivot() {
+        return unPivot;
+    }
+
+    @Override
+    public void setUnPivot(UnPivot unPivot) {
+        this.unPivot = unPivot;
+    }
+
     @Override
     public TableFunction withUnPivot(UnPivot unpivot) {
         return (TableFunction) FromItem.super.withUnPivot(unpivot);
     }
 
+    public StringBuilder appendTo(StringBuilder builder) {
+        if (prefix != null) {
+            builder.append(prefix).append(" ");
+        }
+        builder.append(function.toString());
+
+        if (alias != null) {
+            builder.append(alias);
+        }
+        return builder;
+    }
+
+    @Override
+    public String toString() {
+        return appendTo(new StringBuilder()).toString();
+    }
 }

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

@@ -5063,16 +5063,18 @@ MySQLGroupConcat MySQLGroupConcat():{
 
 TableFunction TableFunction():
 {
-    Alias alias = null;
+    Token prefix = null;
     Function function;
     TableFunction functionItem;
 }
 {
-    function=Function() {
-      functionItem = new TableFunction().withExpression(function);
+    [ prefix = <K_LATERAL> ]
+    function=Function()
+    {
+        return  prefix!=null
+            ? new TableFunction(prefix.image, function)
+            : new TableFunction(function);
     }
-             [LOOKAHEAD(2) alias=Alias() { functionItem.setAlias(alias); }]
-    { return functionItem; }
 }
 
 List<Index.ColumnParams> ColumnNamesWithParamsList() : {

src/test/java/net/sf/jsqlparser/statement/builder/ReflectionModelTest.java

@@ -194,7 +194,7 @@ public class ReflectionModelTest {
             // new net.sf.jsqlparser.statement.select.SetOperationList(),
             new net.sf.jsqlparser.statement.select.Skip(),
             // new net.sf.jsqlparser.statement.select.ParenthesedSelect(),
-            new net.sf.jsqlparser.statement.select.TableFunction(),
+            // new net.sf.jsqlparser.statement.select.TableFunction("LATERAL", new Function()),
             new net.sf.jsqlparser.statement.select.Top(),
             new net.sf.jsqlparser.statement.select.UnPivot(),
             new net.sf.jsqlparser.statement.select.UnionOp(),

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

@@ -3349,7 +3349,7 @@ public void testTableFunctionWithNoParams() throws Exception {
 
         assertTrue(plainSelect.getFromItem() instanceof TableFunction);
         TableFunction fromItem = (TableFunction) plainSelect.getFromItem();
-        Function function = fromItem.getExpression();
+        Function function = fromItem.getFunction();
         assertNotNull(function);
         assertEquals("SOME_FUNCTION", function.getName());
         assertNull(function.getParameters());

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

@@ -0,0 +1,25 @@
+package net.sf.jsqlparser.statement.select;
+
+import net.sf.jsqlparser.JSQLParserException;
+import net.sf.jsqlparser.test.TestUtils;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class TableFunctionTest {
+
+    @Test
+    void testLateralFlat() throws JSQLParserException {
+        String sqlStr = "WITH t AS (\n" +
+                "  SELECT \n" +
+                "    'ABC' AS dim, \n" +
+                "    ARRAY_CONSTRUCT('item1', 'item2', 'item3') AS user_items\n" +
+                ")\n" +
+                "SELECT DIM, count(value) as COUNT_\n" +
+                "FROM t a,\n" +
+                "LATERAL FLATTEN(input => a.user_items) b\n" +
+                "group by 1";
+        TestUtils.assertSqlCanBeParsedAndDeparsed(sqlStr, true);
+    }
+
+}