MDEV-26698: Incorrect row number upon INSERT .. SELECT from the samebb-10.2-MDEV-26698

table: rows are counted twice

Analysis: When the table we are trying to insert into and the SELECT table
are same for INSERT ... SELECT, rows from the SELECT table are copied into
internal temporary table and then to the INSERT table. We only want to
count the rows when we start inserting into the table.
Fix: Reset the counter to 1 before starting to copy from internal temporary
table to select table and then increment the counter.

1 files changed, 25 insertions, 0 deletions

diff --git a/mysql-test/t/insert_select.test b/mysql-test/t/insert_select.test
index 27a831fbe3f..e577f29fd92 100644
--- a/mysql-test/t/insert_select.test
+++ b/mysql-test/t/insert_select.test
@@ -435,3 +435,28 @@ show create table t2;
 drop table t1, t2;
 
 --echo End of 5.5 tests
+
+--echo #
+--echo # Beginning of 10.2 test
+--echo #
+--echo # MDEV-26698: Incorrect row number upon INSERT .. SELECT from the same
+--echo #             table: rows are counted twice
+--echo #
+
+CREATE TABLE t1(a TINYINT);
+
+INSERT INTO t1 VALUES (1), (100);
+
+INSERT INTO t1 SELECT a*2 FROM t1;
+
+TRUNCATE TABLE t1;
+
+--echo # using ORDER BY
+
+INSERT INTO t1 VALUES(1), (2), (100), (3);
+
+INSERT INTO t1 SELECT a*2 FROM t1 ORDER BY a;
+
+DROP TABLE t1;
+
+--echo # End of 10.2 test