From bf0712755884db1627e8dba3df4fec6b53b70d80 Mon Sep 17 00:00:00 2001
From: Kunal Khatua <kkhatua@maprtech.com>
Date: Wed, 10 Apr 2019 12:33:02 -0700
Subject: [PATCH] DRILL-7160: e.q.max_rows QUERY-level option shown even if not
 set

The fix is to force setting to zero IFF autoLimit was intended to be set originally but is inapplicable; such as 'SHOW DATABASES'. If autolimit was not intended to be applied, setting the value to zero is not required.
WebUI is also patched to not show the zero value set in such scenarios.
---
 .../exec/planner/sql/DrillSqlWorker.java      | 24 +++++++++++--------
 .../drill/exec/server/rest/QueryWrapper.java  | 10 +++++++-
 2 files changed, 23 insertions(+), 11 deletions(-)

diff --git a/exec/java-exec/src/main/java/org/apache/drill/exec/planner/sql/DrillSqlWorker.java b/exec/java-exec/src/main/java/org/apache/drill/exec/planner/sql/DrillSqlWorker.java
index dc331d98d32..09fbbdca59a 100644
--- a/exec/java-exec/src/main/java/org/apache/drill/exec/planner/sql/DrillSqlWorker.java
+++ b/exec/java-exec/src/main/java/org/apache/drill/exec/planner/sql/DrillSqlWorker.java
@@ -216,27 +216,31 @@ private static PhysicalPlan getQueryPlan(QueryContext context, String sql, Point
     return handler.getPlan(sqlNode);
   }
 
-  private static boolean isAutoLimitShouldBeApplied(QueryContext context, SqlNode sqlNode) {
-    return (context.getOptions().getOption(ExecConstants.QUERY_MAX_ROWS).num_val.intValue() > 0) && sqlNode.getKind().belongsTo(SqlKind.QUERY)
-        && (sqlNode.getKind() != SqlKind.ORDER_BY || isAutoLimitLessThanOrderByFetch((SqlOrderBy) sqlNode, context));
+  private static boolean isAutoLimitShouldBeApplied(SqlNode sqlNode, int queryMaxRows) {
+    return (queryMaxRows > 0) && sqlNode.getKind().belongsTo(SqlKind.QUERY)
+        && (sqlNode.getKind() != SqlKind.ORDER_BY || isAutoLimitLessThanOrderByFetch((SqlOrderBy) sqlNode, queryMaxRows));
   }
 
   private static SqlNode checkAndApplyAutoLimit(SqlConverter parser, QueryContext context, String sql) {
     SqlNode sqlNode = parser.parse(sql);
-    if (isAutoLimitShouldBeApplied(context, sqlNode)) {
-      sqlNode = wrapWithAutoLimit(sqlNode, context);
+    int queryMaxRows = context.getOptions().getOption(ExecConstants.QUERY_MAX_ROWS).num_val.intValue();
+    if (isAutoLimitShouldBeApplied(sqlNode, queryMaxRows)) {
+      sqlNode = wrapWithAutoLimit(sqlNode, queryMaxRows);
     } else {
-      context.getOptions().setLocalOption(ExecConstants.QUERY_MAX_ROWS, 0);
+      //Force setting to zero IFF autoLimit was intended to be set originally but is inapplicable
+      if (queryMaxRows > 0) {
+        context.getOptions().setLocalOption(ExecConstants.QUERY_MAX_ROWS, 0);
+      }
     }
     return sqlNode;
   }
 
-  private static boolean isAutoLimitLessThanOrderByFetch(SqlOrderBy orderBy, QueryContext context) {
-    return orderBy.fetch == null || Integer.parseInt(orderBy.fetch.toString()) > context.getOptions().getOption(ExecConstants.QUERY_MAX_ROWS).num_val.intValue();
+  private static boolean isAutoLimitLessThanOrderByFetch(SqlOrderBy orderBy, int queryMaxRows) {
+    return orderBy.fetch == null || Integer.parseInt(orderBy.fetch.toString()) > queryMaxRows;
   }
 
-  private static SqlNode wrapWithAutoLimit(SqlNode sqlNode, QueryContext context) {
-    SqlNumericLiteral autoLimitLiteral = SqlLiteral.createExactNumeric(String.valueOf(context.getOptions().getOption(ExecConstants.QUERY_MAX_ROWS).num_val.intValue()), SqlParserPos.ZERO);
+  private static SqlNode wrapWithAutoLimit(SqlNode sqlNode, int queryMaxRows) {
+    SqlNumericLiteral autoLimitLiteral = SqlLiteral.createExactNumeric(String.valueOf(queryMaxRows), SqlParserPos.ZERO);
     if (sqlNode.getKind() == SqlKind.ORDER_BY) {
       SqlOrderBy orderBy = (SqlOrderBy) sqlNode;
       return new SqlOrderBy(orderBy.getParserPosition(), orderBy.query, orderBy.orderList, orderBy.offset, autoLimitLiteral);
diff --git a/exec/java-exec/src/main/java/org/apache/drill/exec/server/rest/QueryWrapper.java b/exec/java-exec/src/main/java/org/apache/drill/exec/server/rest/QueryWrapper.java
index 89315ce60b6..43dd737c908 100644
--- a/exec/java-exec/src/main/java/org/apache/drill/exec/server/rest/QueryWrapper.java
+++ b/exec/java-exec/src/main/java/org/apache/drill/exec/server/rest/QueryWrapper.java
@@ -22,6 +22,7 @@
 
 import org.apache.drill.common.exceptions.UserException;
 import org.apache.drill.common.exceptions.UserRemoteException;
+import org.apache.drill.exec.ExecConstants;
 import org.apache.drill.exec.proto.UserBitShared.QueryId;
 import org.apache.drill.exec.proto.UserBitShared.QueryResult.QueryState;
 import org.apache.drill.exec.proto.UserBitShared.QueryType;
@@ -77,7 +78,14 @@ public QueryResult run(final WorkManager workManager, final WebUserConnection we
         .setAutolimitRowcount(autoLimitRowCount)
         .build();
 
-    webUserConnection.setAutoLimitRowCount(autoLimitRowCount);
+    int defaultMaxRows = webUserConnection.getSession().getOptions().getOption(ExecConstants.QUERY_MAX_ROWS).num_val.intValue();
+    int maxRows;
+    if (autoLimitRowCount > 0 && defaultMaxRows > 0) {
+      maxRows = Math.min(autoLimitRowCount, defaultMaxRows);
+    } else {
+      maxRows = Math.max(autoLimitRowCount, defaultMaxRows);
+    }
+    webUserConnection.setAutoLimitRowCount(maxRows);
 
     // Submit user query to Drillbit work queue.
     final QueryId queryId = workManager.getUserWorker().submitWork(webUserConnection, runQuery);