Encode varbinary literals as a function call to from_base64(...)

They were being encoded using the "magic literal" hack, but the value
was being encoded as a UTF-8 string. The magic literal evaluator doesn't
know it has to reverse the process, so this ends up corrupting varbinary
literals during constant folding or distributed evaluation.

This minor hack turns varbinary literals into function calls to:

  from_base64(<base64-encoded varchar>)

presto-main/src/main/java/com/facebook/presto/sql/planner/LiteralInterpreter.java

@@ -17,6 +17,7 @@
 import com.facebook.presto.metadata.FunctionRegistry;
 import com.facebook.presto.metadata.Metadata;
 import com.facebook.presto.metadata.Signature;
+import com.facebook.presto.operator.scalar.VarbinaryFunctions;
 import com.facebook.presto.spi.ConnectorSession;
 import com.facebook.presto.spi.type.Type;
 import com.facebook.presto.sql.analyzer.SemanticException;
@@ -46,6 +47,7 @@
 import static com.facebook.presto.spi.type.BooleanType.BOOLEAN;
 import static com.facebook.presto.spi.type.DoubleType.DOUBLE;
 import static com.facebook.presto.spi.type.TypeSignature.parseTypeSignature;
+import static com.facebook.presto.spi.type.VarbinaryType.VARBINARY;
 import static com.facebook.presto.spi.type.VarcharType.VARCHAR;
 import static com.facebook.presto.sql.analyzer.SemanticErrorCode.TYPE_MISMATCH;
 import static com.facebook.presto.type.UnknownType.UNKNOWN;
@@ -134,6 +136,13 @@ else if (value.equals(Double.POSITIVE_INFINITY)) {
  return new BooleanLiteral(object.toString());
  }
 
+ if (type.equals(VARBINARY) && object instanceof Slice) {
+ // HACK: we need to serialize VARBINARY in a format that can be embedded in an expression to be
+ // able to encode it in the plan that gets sent to workers.
+ // We do this by transforming the in-memory varbinary into a call to from_base64(<base64-encoded value>)
+ return new FunctionCall(new QualifiedName("from_base64"), ImmutableList.of(new StringLiteral(VarbinaryFunctions.toBase64((Slice) object).toStringUtf8())));
+ }
+
  Signature signature = FunctionRegistry.getMagicLiteralFunctionSignature(type);
  Expression rawLiteral = toExpression(object, FunctionRegistry.type(type.getJavaType()));
  return new FunctionCall(new QualifiedName(signature.getName()), ImmutableList.of(rawLiteral));

presto-tests/src/main/java/com/facebook/presto/tests/AbstractTestQueries.java

@@ -91,6 +91,14 @@ public void selectNull()
  assertQuery("SELECT NULL", "SELECT NULL FROM (SELECT * FROM ORDERS LIMIT 1)");
  }
 
+ @Test
+ public void testVarbinary()
+ throws Exception
+ {
+ assertQuery("SELECT LENGTH(x) FROM (SELECT from_base64('gw==') as x)", "SELECT 1");
+ assertQuery("SELECT LENGTH(from_base64('gw=='))", "SELECT 1");
+ }
+
  @Test
  public void testRowFieldAccessor()
  throws Exception