From f863c653e26dc3d32ee28ae00352152123b5ae90 Mon Sep 17 00:00:00 2001
From: LiBinfeng <46676950+LiBinfeng-01@users.noreply.github.com>
Date: Thu, 13 Jul 2023 11:17:28 +0800
Subject: [PATCH] [Fix](Planner) fix limit execute before sort in show export
 job (#21663)

Problem:
When doing show export jobs, limit would execute before sort before changed. So the result would not be expected because limit always cut results first and we can not get what we want.

Example:
we having export job1 and job2 with JobId1 > JobId2. We want to get job with JobId1
show export from db order by JobId desc limit 1;
We do limit 1 first, so we would probably get Job2 because JobId assigned from small to large

Solve:
We can not cut results first if we have order by clause. And cut result set after sorting
---
 .../java/org/apache/doris/load/ExportMgr.java |  6 ++-
 .../suites/export_p0/test_export_basic.groovy | 43 +++++++++++++++++++
 2 files changed, 48 insertions(+), 1 deletion(-)

diff --git a/fe/fe-core/src/main/java/org/apache/doris/load/ExportMgr.java b/fe/fe-core/src/main/java/org/apache/doris/load/ExportMgr.java
index a81144138e..0e0b26f273 100644
--- a/fe/fe-core/src/main/java/org/apache/doris/load/ExportMgr.java
+++ b/fe/fe-core/src/main/java/org/apache/doris/load/ExportMgr.java
@@ -307,7 +307,7 @@ public class ExportMgr extends MasterDaemon {
                     exportJobInfos.add(composeExportJobInfo(job));
                 }
 
-                if (++counter >= resultNum) {
+                if (++counter >= resultNum && orderByPairs == null) {
                     break;
                 }
             }
@@ -327,8 +327,12 @@ public class ExportMgr extends MasterDaemon {
         Collections.sort(exportJobInfos, comparator);
 
         List<List<String>> results = Lists.newArrayList();
+        int counter = 0;
         for (List<Comparable> list : exportJobInfos) {
             results.add(list.stream().map(e -> e.toString()).collect(Collectors.toList()));
+            if (++counter >= resultNum) {
+                break;
+            }
         }
 
         return results;
diff --git a/regression-test/suites/export_p0/test_export_basic.groovy b/regression-test/suites/export_p0/test_export_basic.groovy
index 07c3168c5d..95805db491 100644
--- a/regression-test/suites/export_p0/test_export_basic.groovy
+++ b/regression-test/suites/export_p0/test_export_basic.groovy
@@ -386,4 +386,47 @@ suite("test_export_basic", "p0") {
         try_sql("DROP TABLE IF EXISTS ${table_load_name}")
         delete_files.call("${outFilePath}")
     }
+
+    // 5. test order by and limit clause
+    uuid1 = UUID.randomUUID().toString()
+    outFilePath = """${outfile_path_prefix}_${uuid1}"""
+    label1 = "label_${uuid1}"
+    uuid2 = UUID.randomUUID().toString()
+    label2 = "label_${uuid2}"
+    try {
+        // check export path
+        check_path_exists.call("${outFilePath}")
+
+        // exec export
+        sql """
+            EXPORT TABLE ${table_export_name} PARTITION (less_than_20)
+            TO "file://${outFilePath}/"
+            PROPERTIES(
+                "label" = "${label1}",
+                "format" = "csv",
+                "column_separator"=","
+            );
+        """
+        sql """
+            EXPORT TABLE ${table_export_name} PARTITION (between_20_70)
+            TO "file://${outFilePath}/"
+            PROPERTIES(
+                "label" = "${label2}",
+                "format" = "csv",
+                "column_separator"=","
+            );
+        """
+        waiting_export.call(label1)
+        waiting_export.call(label2)
+
+        // check file amounts
+        check_file_amounts.call("${outFilePath}", 2)
+
+        // check show export correctness
+        def res = sql """ show export where STATE = "FINISHED" order by JobId desc limit 2"""
+        assertTrue(res[0][0] > res[1][0])
+
+    } finally {
+        delete_files.call("${outFilePath}")
+    }
 }