MDEV-18904 Assertion `m_part_spec.start_part >= m_part_spec.end_part' failed...

MDEV-18904 Assertion `m_part_spec.start_part >= m_part_spec.end_part' failed in ha_partition::index_read_idx_map

Remove the DBUG_ASSERT

mysql-test/main/long_unique_bugs.result

@@ -235,3 +235,7 @@ ERROR 23000: Duplicate entry '
 insert into t1 values ('ббб');
 ERROR 23000: Duplicate entry '' for key 'a'
 drop table t1;
+CREATE TABLE t1 (a INT, UNIQUE USING HASH (a)) PARTITION BY HASH (a) PARTITIONS 2;
+INSERT INTO t1 VALUES (2);
+REPLACE INTO t1 VALUES (2);
+DROP TABLE t1;

mysql-test/main/long_unique_bugs.test

@@ -265,3 +265,12 @@ insert into t1 values ('бб');
 --error ER_DUP_ENTRY
 insert into t1 values ('ббб');
 drop table t1;
+
+#
+# MDEV-18904 Assertion `m_part_spec.start_part >= m_part_spec.end_part' failed in ha_partition::index_read_idx_map
+#
+--source include/have_partition.inc
+CREATE TABLE t1 (a INT, UNIQUE USING HASH (a)) PARTITION BY HASH (a) PARTITIONS 2;
+INSERT INTO t1 VALUES (2);
+REPLACE INTO t1 VALUES (2);
+DROP TABLE t1;

sql/ha_partition.cc

@@ -5759,12 +5759,6 @@ int ha_partition::index_read_idx_map(uchar *buf, uint index,
 
     get_partition_set(table, buf, index, &m_start_key, &m_part_spec);
 
-    /*
-      We have either found exactly 1 partition
-      (in which case start_part == end_part)
-      or no matching partitions (start_part > end_part)
-    */
-    DBUG_ASSERT(m_part_spec.start_part >= m_part_spec.end_part);
     /* The start part is must be marked as used. */
     DBUG_ASSERT(m_part_spec.start_part > m_part_spec.end_part ||
                 bitmap_is_set(&(m_part_info->read_partitions),