[incubator-iotdb] branch master updated: [IOTDB-153]further limit fetchSize to speed up LIMIT&OFFSET query (#302)

[qi...@apache.org]

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qiaojialin pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/incubator-iotdb.git


The following commit(s) were added to refs/heads/master by this push:
     new 4ac6d7e  [IOTDB-153]further limit fetchSize to speed up LIMIT&OFFSET query (#302)
4ac6d7e is described below

commit 4ac6d7eb0cadab05f63732b8aa9c585e6a900d38
Author: RUI, LEI <33...@users.noreply.github.com>
AuthorDate: Fri Jul 26 09:47:16 2019 +0800

    [IOTDB-153]further limit fetchSize to speed up LIMIT&OFFSET query (#302)
    
    * further limit fetchSize to speed up LIMIT clause
---
 .../java/org/apache/iotdb/jdbc/IoTDBQueryResultSet.java    | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/jdbc/src/main/java/org/apache/iotdb/jdbc/IoTDBQueryResultSet.java b/jdbc/src/main/java/org/apache/iotdb/jdbc/IoTDBQueryResultSet.java
index 0c0198a..632e1b1 100644
--- a/jdbc/src/main/java/org/apache/iotdb/jdbc/IoTDBQueryResultSet.java
+++ b/jdbc/src/main/java/org/apache/iotdb/jdbc/IoTDBQueryResultSet.java
@@ -701,9 +701,10 @@ public class IoTDBQueryResultSet implements ResultSet {
   }
 
   // the next record rule without constraints
-  private boolean nextWithoutConstraints() throws SQLException {
+  private boolean nextWithoutConstraints(int limitFetchSize) throws SQLException {
     if ((recordItr == null || !recordItr.hasNext()) && !emptyResultSet) {
-      TSFetchResultsReq req = new TSFetchResultsReq(sql, fetchSize, queryId);
+      int adaFetchSize = (limitFetchSize < fetchSize) ? limitFetchSize : fetchSize;
+      TSFetchResultsReq req = new TSFetchResultsReq(sql, adaFetchSize, queryId);
 
       try {
         TSFetchResultsResp resp = client.fetchResults(req);
@@ -743,14 +744,19 @@ public class IoTDBQueryResultSet implements ResultSet {
     // When rowsOffset is constrained and the offset position has NOT been reached
     if (rowsOffset != 0) {
       for (int i = 0; i < rowsOffset; i++) { // Try to move to the offset position
-        if (!nextWithoutConstraints()) {
+        if (!nextWithoutConstraints(rowsOffset + maxRowsOrRowsLimit - i)) {
           return false; // No next record, i.e, fail to move to the offset position
         }
       }
       rowsOffset = 0; // The offset position has been reached
     }
 
-    boolean isNext = nextWithoutConstraints();
+    boolean isNext;
+    if (maxRowsOrRowsLimit > 0) {
+      isNext = nextWithoutConstraints(maxRowsOrRowsLimit - rowsFetched);
+    } else { // maxRowsOrRowsLimit=0 means neither maxRows nor LIMIT is constrained.
+      isNext = nextWithoutConstraints(fetchSize);
+    }
 
     if (isNext) {
       /*