HIVE-8295 : Add batch retrieve partition objects for metastore direct…

… sql (Selina Zhang and Sergey Shelukhin, reviewed by Ashutosh Chauhan)

git-svn-id: https://svn.apache.org/repos/asf/hive/trunk@1639500 13f79535-47bb-0310-9956-ffa450edef68

common/src/java/org/apache/hadoop/hive/conf/HiveConf.java

@@ -510,6 +510,11 @@ public static enum ConfVars {
         "work for all queries on your datastore. If all SQL queries fail (for example, your\n" +
         "metastore is backed by MongoDB), you might want to disable this to save the\n" +
         "try-and-fall-back cost."),
+    METASTORE_DIRECT_SQL_PARTITION_BATCH_SIZE("hive.metastore.direct.sql.batch.size", 0,
+        "Batch size for partition and other object retrieval from the underlying DB in direct\n" +
+        "SQL. For some DBs like Oracle and MSSQL, there are hardcoded or perf-based limitations\n" +
+        "that necessitate this. For DBs that can handle the queries, this isn't necessary and\n" +
+        "may impede performance. -1 means no batching, 0 means automatic batching."),
     METASTORE_TRY_DIRECT_SQL_DDL("hive.metastore.try.direct.sql.ddl", true,
         "Same as hive.metastore.try.direct.sql, for read statements within a transaction that\n" +
         "modifies metastore data. Due to non-standard behavior in Postgres, if a direct SQL\n" +