[SPARK-11103][SQL] Disable predicate push down when using merged schema for Parquet.

Author: HyukjinKwon

sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetRelation.scala

@@ -292,6 +292,10 @@ private[sql] class ParquetRelation(
     val assumeBinaryIsString = sqlContext.conf.isParquetBinaryAsString
     val assumeInt96IsTimestamp = sqlContext.conf.isParquetINT96AsTimestamp
 
+    // When using merged schema and the column of the given filter does not exist, Parquet emits
+    // an error which is an issue of Parquet (PARQUET-389).
+    val safeParquetFilterPushDown = !shouldMergeSchemas && parquetFilterPushDown
+
     // Parquet row group size. We will use this value as the value for
     // mapreduce.input.fileinputformat.split.minsize and mapred.min.split.size if the value
     // of these flags are smaller than the parquet row group size.
@@ -305,7 +309,7 @@ private[sql] class ParquetRelation(
         dataSchema,
         parquetBlockSize,
         useMetadataCache,
-        parquetFilterPushDown,
+        safeParquetFilterPushDown,
         assumeBinaryIsString,
         assumeInt96IsTimestamp) _