Quote potentially ambiguous symbol references in EXPLAIN

core/trino-main/src/main/java/io/trino/sql/ir/ExpressionFormatter.java

@@ -13,6 +13,7 @@
  */
 package io.trino.sql.ir;
 
+import com.google.common.base.CharMatcher;
 import com.google.common.base.Joiner;
 import com.google.common.collect.ImmutableList;
 import io.trino.sql.planner.Symbol;
@@ -26,6 +27,13 @@
 
 public final class ExpressionFormatter
 {
+    private static final CharMatcher UNAMBIGUOUS_REFERENCE_NAME_CHARACTERS =
+            CharMatcher.inRange('a', 'z')
+                    .or(CharMatcher.inRange('A', 'Z'))
+                    .or(CharMatcher.inRange('0', '9'))
+                    .or(CharMatcher.anyOf("_$"))
+                    .precomputed();
+
     private ExpressionFormatter() {}
 
     public static String formatExpression(Expression expression)
@@ -105,7 +113,11 @@ protected String visitReference(Reference node, Void context)
             if (symbolReferenceFormatter.isPresent()) {
                 return symbolReferenceFormatter.get().apply(node);
             }
-            return node.name();
+            String name = node.name();
+            if (UNAMBIGUOUS_REFERENCE_NAME_CHARACTERS.matchesAllOf(name)) {
+                return name;
+            }
+            return "\"" + name.replace("\"", "\"\"") + "\"";
         }
 
         @Override

core/trino-main/src/test/java/io/trino/sql/ir/TestExpressionFormatter.java

@@ -0,0 +1,42 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package io.trino.sql.ir;
+
+import org.junit.jupiter.api.Test;
+
+import static io.trino.spi.type.BigintType.BIGINT;
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class TestExpressionFormatter
+{
+    @Test
+    public void testReference()
+    {
+        assertFormattedExpression(
+                new Reference(BIGINT, "abc"),
+                "abc");
+        assertFormattedExpression(
+                new Reference(BIGINT, "with a space"),
+                "\"with a space\"");
+        assertFormattedExpression(
+                new Reference(BIGINT, "with \" quote, $ dollar and ' apostrophe"),
+                "\"with \"\" quote, $ dollar and ' apostrophe\"");
+    }
+
+    private void assertFormattedExpression(Expression expression, String expected)
+    {
+        assertThat(ExpressionFormatter.formatExpression(expression)).as("formatted expression")
+                .isEqualTo(expected);
+    }
+}

core/trino-parser/src/test/java/io/trino/sql/TestExpressionFormatter.java

@@ -15,6 +15,7 @@
 
 import io.trino.sql.tree.Expression;
 import io.trino.sql.tree.GenericLiteral;
+import io.trino.sql.tree.Identifier;
 import io.trino.sql.tree.IntervalLiteral;
 import io.trino.sql.tree.StringLiteral;
 import org.junit.jupiter.api.Test;
@@ -30,6 +31,20 @@
 
 public class TestExpressionFormatter
 {
+    @Test
+    public void testIdentifier()
+    {
+        assertFormattedExpression(
+                new Identifier("abc"),
+                "abc");
+        assertFormattedExpression(
+                new Identifier("with a space"),
+                "\"with a space\"");
+        assertFormattedExpression(
+                new Identifier("with \" quote, $ dollar and ' apostrophe"),
+                "\"with \"\" quote, $ dollar and ' apostrophe\"");
+    }
+
     @Test
     public void testStringLiteral()
     {