Bug#26827 - table->read_set is set incorrectly,

          causing update of a different column

For efficiency some storage engines do not read a complete record
for update, but only the columns required for selecting the rows.

When updating a row of a partitioned table, modifying a column
that is part of the partition or subpartition expression, then
the row may need to move from one [sub]partition to another one.
This is done by inserting the new row into the target
[sub]partition and deleting the old row from the originating one.
For the insert we need a complete record.

If an above mentioned engine was used for a partitioned table, we
did not have a complete record in update_row(). The implicitly
executed write_row() got an incomplete record.

This is solved by instructing the engine to read a complete record
if one of the columns of the partition or subpartiton is to be
updated.

No testcase. This can be reproduced with Falcon only. The engines
contained in standard 5.1 do always return complete records on
update.


sql/ha_partition.cc:
  Bug#26827 - table->read_set is set incorrectly,
              causing update of a different column
  Setting partition field bits in read_set if a writing
  operation is going on. This replaces the old function
  include_partition_fields_in_used_fields().
  Setting all bits in read_set if write_set contains a column
  used in a partition or subpartition expression.
  Removed include_partition_fields_in_used_fields().
sql/ha_partition.h:
  Bug#26827 - table->read_set is set incorrectly,
              causing update of a different column
  Removed declaration of
  include_partition_fields_in_used_fields().
sql/partition_info.h:
  Bug#26827 - table->read_set is set incorrectly,
              causing update of a different column
  Added a bitmap to partition_info for a quick check of
  columns used in a partition or subpartition expression.
sql/sql_partition.cc:
  Bug#26827 - table->read_set is set incorrectly,
              causing update of a different column
  Initializing the new bitmap with all columns used in a
  partition or subpartition expression.

1 files changed, 37 insertions, 32 deletions

diff --git a/sql/ha_partition.cc b/sql/ha_partition.cc
index 31f59c662d4..e4924e8e8f2 100644
--- a/sql/ha_partition.cc
+++ b/sql/ha_partition.cc
@@ -2961,8 +2961,34 @@ int ha_partition::rnd_init(bool scan)
   uint32 part_id;
   DBUG_ENTER("ha_partition::rnd_init");
 
-  include_partition_fields_in_used_fields();
-  
+  /*
+    For operations that may need to change data, we may need to extend
+    read_set.
+  */
+  if (m_lock_type == F_WRLCK)
+  {
+    /*
+      If write_set contains any of the fields used in partition and
+      subpartition expression, we need to set all bits in read_set because
+      the row may need to be inserted in a different [sub]partition. In
+      other words update_row() can be converted into write_row(), which
+      requires a complete record.
+    */
+    if (bitmap_is_overlapping(&m_part_info->full_part_field_set,
+                              table->write_set))
+      bitmap_set_all(table->read_set);
+    else
+    {
+      /*
+        Some handlers only read fields as specified by the bitmap for the
+        read set. For partitioned handlers we always require that the
+        fields of the partition functions are read such that we can
+        calculate the partition id to place updated and deleted records.
+      */
+      bitmap_union(table->read_set, &m_part_info->full_part_field_set);
+    }
+  }
+
   /* Now we see what the index of our first important partition is */
   DBUG_PRINT("info", ("m_part_info->used_partitions: 0x%lx",
                       (long) m_part_info->used_partitions.bitmap));
@@ -3276,7 +3302,15 @@ int ha_partition::index_init(uint inx, bool sorted)
   m_start_key.length= 0;
   m_ordered= sorted;
   m_curr_key_info= table->key_info+inx;
-  include_partition_fields_in_used_fields();
+  /*
+    Some handlers only read fields as specified by the bitmap for the
+    read set. For partitioned handlers we always require that the
+    fields of the partition functions are read such that we can
+    calculate the partition id to place updated and deleted records.
+    But this is required for operations that may need to change data only.
+  */
+  if (m_lock_type == F_WRLCK)
+    bitmap_union(table->read_set, &m_part_info->full_part_field_set);
   file= m_file;
   do
   {
@@ -4145,35 +4179,6 @@ int ha_partition::handle_ordered_prev(uchar *buf)
 }
 
 
-/*
-  Set fields in partition functions in read set for underlying handlers
-
-  SYNOPSIS
-    include_partition_fields_in_used_fields()
-
-  RETURN VALUE
-    NONE
-
-  DESCRIPTION
-    Some handlers only read fields as specified by the bitmap for the
-    read set. For partitioned handlers we always require that the
-    fields of the partition functions are read such that we can
-    calculate the partition id to place updated and deleted records.
-*/
-
-void ha_partition::include_partition_fields_in_used_fields()
-{
-  Field **ptr= m_part_field_array;
-  DBUG_ENTER("ha_partition::include_partition_fields_in_used_fields");
-
-  do
-  {
-    bitmap_set_bit(table->read_set, (*ptr)->field_index);
-  } while (*(++ptr));
-  DBUG_VOID_RETURN;
-}
-
-
 /****************************************************************************
                 MODULE information calls
 ****************************************************************************/