feat: DuckDB Lambda Functions

- at the moment, only one lambda parameter is supported, sorry

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

Author: manticore-projects

src/main/java/net/sf/jsqlparser/expression/ExpressionVisitor.java

@@ -247,4 +247,6 @@ public interface ExpressionVisitor {
     void visit(TSQLRightJoin tsqlRightJoin);
 
     void visit(StructType structType);
+
+    void visit(LambdaExpression lambdaExpression);
 }

src/main/java/net/sf/jsqlparser/expression/ExpressionVisitorAdapter.java

@@ -702,4 +702,9 @@ public void visit(StructType structType) {
         }
     }
 
+    @Override
+    public void visit(LambdaExpression lambdaExpression) {
+        lambdaExpression.getExpression().accept(this);
+    }
+
 }

src/main/java/net/sf/jsqlparser/expression/LambdaExpression.java

@@ -0,0 +1,57 @@
+package net.sf.jsqlparser.expression;
+
+import net.sf.jsqlparser.parser.ASTNodeAccessImpl;
+
+import java.util.List;
+
+public class LambdaExpression extends ASTNodeAccessImpl implements Expression {
+    private List<String> identifiers;
+    private Expression expression;
+
+    public LambdaExpression(List<String> identifiers, Expression expression) {
+        this.identifiers = identifiers;
+        this.expression = expression;
+    }
+
+    public List<String> getIdentifiers() {
+        return identifiers;
+    }
+
+    public LambdaExpression setIdentifiers(List<String> identifiers) {
+        this.identifiers = identifiers;
+        return this;
+    }
+
+    public Expression getExpression() {
+        return expression;
+    }
+
+    public LambdaExpression setExpression(Expression expression) {
+        this.expression = expression;
+        return this;
+    }
+
+    public StringBuilder appendTo(StringBuilder builder) {
+        if (identifiers.size() == 1) {
+            builder.append(identifiers.get(0));
+        } else {
+            int i = 0;
+            builder.append("( ");
+            for (String s : identifiers) {
+                builder.append(i++ > 0 ? ", " : "").append(s);
+            }
+            builder.append(" )");
+        }
+        return builder.append(" -> ").append(expression);
+    }
+
+    @Override
+    public String toString() {
+        return appendTo(new StringBuilder()).toString();
+    }
+
+    @Override
+    public void accept(ExpressionVisitor expressionVisitor) {
+        expressionVisitor.visit(this);
+    }
+}

src/main/java/net/sf/jsqlparser/util/TablesNamesFinder.java

@@ -41,6 +41,7 @@
 import net.sf.jsqlparser.expression.JsonFunction;
 import net.sf.jsqlparser.expression.JsonFunctionExpression;
 import net.sf.jsqlparser.expression.KeepExpression;
+import net.sf.jsqlparser.expression.LambdaExpression;
 import net.sf.jsqlparser.expression.LongValue;
 import net.sf.jsqlparser.expression.MySQLGroupConcat;
 import net.sf.jsqlparser.expression.NextValExpression;
@@ -1187,6 +1188,11 @@ public void visit(StructType structType) {
         }
     }
 
+    @Override
+    public void visit(LambdaExpression lambdaExpression) {
+        lambdaExpression.getExpression().accept(this);
+    }
+
     @Override
     public void visit(VariableAssignment var) {
         var.getVariable().accept(this);

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

@@ -35,6 +35,7 @@
 import net.sf.jsqlparser.expression.JsonExpression;
 import net.sf.jsqlparser.expression.JsonFunction;
 import net.sf.jsqlparser.expression.KeepExpression;
+import net.sf.jsqlparser.expression.LambdaExpression;
 import net.sf.jsqlparser.expression.LongValue;
 import net.sf.jsqlparser.expression.MySQLGroupConcat;
 import net.sf.jsqlparser.expression.NextValExpression;
@@ -1179,4 +1180,21 @@ public void visit(StructType structType) {
         }
     }
 
+    @Override
+    public void visit(LambdaExpression lambdaExpression) {
+        if (lambdaExpression.getIdentifiers().size() == 1) {
+            buffer.append(lambdaExpression.getIdentifiers().get(0));
+        } else {
+            int i = 0;
+            buffer.append("( ");
+            for (String s : lambdaExpression.getIdentifiers()) {
+                buffer.append(i++ > 0 ? ", " : "").append(s);
+            }
+            buffer.append(" )");
+        }
+
+        buffer.append(" -> ");
+        lambdaExpression.getExpression().accept(this);
+    }
+
 }

src/main/java/net/sf/jsqlparser/util/validation/validator/ExpressionValidator.java

@@ -34,6 +34,7 @@
 import net.sf.jsqlparser.expression.JsonExpression;
 import net.sf.jsqlparser.expression.JsonFunction;
 import net.sf.jsqlparser.expression.KeepExpression;
+import net.sf.jsqlparser.expression.LambdaExpression;
 import net.sf.jsqlparser.expression.LongValue;
 import net.sf.jsqlparser.expression.MySQLGroupConcat;
 import net.sf.jsqlparser.expression.NextValExpression;
@@ -719,4 +720,9 @@ public void visit(StructType structType) {
             }
         }
     }
+
+    @Override
+    public void visit(LambdaExpression lambdaExpression) {
+        lambdaExpression.getExpression().accept(this);
+    }
 }

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

@@ -3879,7 +3879,7 @@ ExpressionList SimpleExpressionList():
 }
 {
     expr=SimpleExpression() { expressions.add(expr); }
-    ( LOOKAHEAD(2, {!interrupted} ) "," expr=SimpleExpression() { expressions.add(expr); } )*
+    ( LOOKAHEAD(2, {!interrupted} ) "," ( LOOKAHEAD(2) expr=LambdaExpression() | expr=SimpleExpression()) { expressions.add(expr); } )*
     {
         return expressions;
     }
@@ -3928,6 +3928,7 @@ ExpressionList ComplexExpressionList():
         LOOKAHEAD(2, {!interrupted}) ","
         (
             LOOKAHEAD(2) expr=OracleNamedFunctionParameter()
+            | LOOKAHEAD(2) expr=LambdaExpression()
             | expr=Expression()
         ) { expressions.add(expr); }
     )*
@@ -5202,6 +5203,35 @@ FullTextSearch FullTextSearch() : {
     }
 }
 
+LambdaExpression LambdaExpression() #LambdaExpression:
+{
+    String s;
+    ArrayList<String> identifiers = new ArrayList<String>();
+    Expression expression;
+    LambdaExpression lambdaExpression;
+}
+{
+//    wip, right now the Grammar works but collides with Multi Value Lists
+//    (
+//        LOOKAHEAD(3) "("
+//        s = RelObjectName() { identifiers.add(s); }
+//        ( "," s = RelObjectName() { identifiers.add(s); } )*
+//        ")"
+//    )
+//    |
+    (
+        s = RelObjectName() { identifiers.add(s); }
+    )
+
+    "->"
+    expression = Expression()
+    {
+        lambdaExpression = new LambdaExpression(identifiers, expression);
+        linkAST(lambdaExpression,jjtThis);
+        return lambdaExpression;
+    }
+}
+
 Function Function() #Function:
 {
     Function function;

src/test/java/net/sf/jsqlparser/expression/LambdaExpressionTest.java

@@ -0,0 +1,29 @@
+package net.sf.jsqlparser.expression;
+
+import net.sf.jsqlparser.JSQLParserException;
+import net.sf.jsqlparser.test.TestUtils;
+import org.junit.jupiter.api.Disabled;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class LambdaExpressionTest {
+
+    @Test
+    void testLambdaFunctionSingleParameter() throws JSQLParserException {
+        String sqlStr = "select list_transform( split('test', ''),  x -> unicode(x) )";
+        TestUtils.assertSqlCanBeParsedAndDeparsed(sqlStr, true);
+    }
+
+    @Disabled
+    @Test
+    // wip, right now the Grammar works but collides with Multi Value Lists
+    void testLambdaFunctionMultipleParameter() throws JSQLParserException {
+        String sqlStr = "SELECT list_transform(\n" +
+                "        [1, 2, 3],\n" +
+                "        x -> list_reduce([4, 5, 6], (a, b) -> a + b) + x\n" +
+                "    )";
+        TestUtils.assertSqlCanBeParsedAndDeparsed(sqlStr, true);
+    }
+
+}