Change create_field->offset to store offset from start of fields, independent of null bits.

Count null_bits separately from field offsets and adjust them in case of primary key parts.
(Previously a CREATE TABLE with a lot of null fields that was part of a primary key caused MySQL to wrongly count the number of bytes needed to store null bits)
This is a more complete bug fix for #6236


mysql-test/r/alter_table.result:
  More test for bug #6236 (CREATE TABLE didn't properly count not null columns for primary keys)
mysql-test/t/alter_table.test:
  More test for bug #6236 (CREATE TABLE didn't properly count not null columns for primary keys)
sql/handler.h:
  Add counter for null fields
sql/sql_table.cc:
  Change create_field->offset to store offset from start of fields, independent of null bits.
  Count null_bits separately from field offsets and adjust them in case of primary key parts.
sql/unireg.cc:
  Change create_field->offset to store offset from start of fields, independent of null bits.
  Count null_bits separately from field offsets and adjust them in case of primary key parts.

1 files changed, 1 insertions, 0 deletions

diff --git a/sql/handler.h b/sql/handler.h
index ac00050b777..e52164a871a 100644
--- a/sql/handler.h
+++ b/sql/handler.h
@@ -164,6 +164,7 @@ typedef struct st_ha_create_information
   SQL_LIST merge_list;
   enum db_type db_type;
   enum row_type row_type;
+  uint null_bits;                       /* NULL bits at start of record */
   uint options;				/* OR of HA_CREATE_ options */
   uint raid_type,raid_chunks;
   uint merge_insert_method;