update the document

Author: gatorsmile

sql/core/src/main/scala/org/apache/spark/sql/internal/SQLConf.scala

@@ -215,7 +215,8 @@ object SQLConf {
     .createWithDefault("snappy")
 
   val PARQUET_FILTER_PUSHDOWN_ENABLED = SQLConfigBuilder("spark.sql.parquet.filterPushdown")
-    .doc("Enables Parquet filter push-down optimization when set to true.")
+    .doc("Enables Parquet filter push-down optimization when set to true and vectorized parquet " +
+      "decoding is not being used.")
     .booleanConf
     .createWithDefault(true)
 
@@ -236,7 +237,8 @@ object SQLConf {
 
   val PARQUET_VECTORIZED_READER_ENABLED =
     SQLConfigBuilder("spark.sql.parquet.enableVectorizedReader")
-      .doc("Enables vectorized parquet decoding.")
+      .doc("Enables vectorized parquet decoding when set to true and all the data types of " +
+        "the table schemas are atomic types.")
       .booleanConf
       .createWithDefault(true)
 

sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetFilterSuite.scala

@@ -553,6 +553,7 @@ class ParquetFilterSuite extends QueryTest with ParquetTest with SharedSQLContex
       // When SQLConf.PARQUET_VECTORIZED_READER_ENABLED.key is set to true and all the data types
       // of the table schema are AtomicType, the parquet reader uses vectorizedReader.
       // In this mode, filters will not be pushed down, no matter whether
+      // SQLConf.PARQUET_FILTER_PUSHDOWN_ENABLED.key is true or not.
       withSQLConf(SQLConf.PARQUET_FILTER_PUSHDOWN_ENABLED.key -> pushDown,
           SQLConf.PARQUET_VECTORIZED_READER_ENABLED.key -> "false") {
         withTempPath { dir =>