1. 23 Mar, 2007 1 commit
  2. 21 Mar, 2007 1 commit
  3. 19 Mar, 2007 2 commits
    • unknown's avatar
      sql_insert.cc: · 3798a7d5
      unknown authored
        Removed wrong fix for the bug#27006.
        The bug was added by the fix for the bug#19978 and fixed by Monty on 2007/02/21.
      trigger.test, trigger.result:
        Corrected test case for the bug#27006.
      
      
      sql/sql_insert.cc:
        Removed wrong fix for the bug#27006.
        The bug was added by the fix for the bug#19978 and fixed by Monty on 2007/02/21.
      mysql-test/t/trigger.test:
        Corrected test case for the bug#27006.
      mysql-test/r/trigger.result:
        Corrected test case for the bug#27006.
      3798a7d5
    • unknown's avatar
      Merge bk-internal.mysql.com:/home/bk/mysql-5.0 · 14ab9bef
      unknown authored
      into  bodhi.local:/opt/local/work/mysql-5.0-runtime
      
      
      sql/field.cc:
        Auto merged
      sql/item.cc:
        Auto merged
      sql/item.h:
        Auto merged
      sql/item_func.cc:
        Auto merged
      sql/sp_head.cc:
        Auto merged
      sql/sql_base.cc:
        Auto merged
      sql/sql_select.cc:
        Auto merged
      sql/sql_show.cc:
        Auto merged
      sql/sql_table.cc:
        Auto merged
      sql/sql_yacc.yy:
        Auto merged
      mysql-test/r/sp.result:
        SCCS merged
      mysql-test/t/sp.test:
        SCCS merged
      14ab9bef
  4. 16 Mar, 2007 8 commits
    • unknown's avatar
      Bug#27006: AFTER UPDATE triggers not fired with INSERT ... ON DUPLICATE KEY · 6d93f150
      unknown authored
      UPDATE if the row wasn't actually changed.
      
      This bug was caused by fix for bug#19978. It causes AFTER UPDATE triggers
      not firing if a row wasn't actually changed by the update part of the
      INSERT .. ON DUPLICATE KEY UPDATE.
      
      Now triggers are always fired if a row is touched by the INSERT ... ON
      DUPLICATE KEY UPDATE.
      
      
      sql/sql_insert.cc:
        Bug#27006: AFTER UPDATE triggers not fired with INSERT ... ON DUPLICATE KEY
        UPDATE if the row wasn't actually changed.
        Now triggers are always fired if a row is touched by the INSERT ... ON
        DUPLICATE KEY UPDATE.
      mysql-test/r/trigger.result:
        Added a test case for the bug#27006: AFTER UPDATE triggers not fired with INSERT ... ON DUPLICATE KEY
        UPDATE if the row wasn't actually changed.
      mysql-test/t/trigger.test:
        Added a test case for the bug#27006: AFTER UPDATE triggers not fired with INSERT ... ON DUPLICATE KEY
        UPDATE if the row wasn't actually changed.
      6d93f150
    • unknown's avatar
      Bug#20777 Function w BIGINT UNSIGNED shows diff. behaviour with and without --ps-protocol · ffc605aa
      unknown authored
      - Stored procedures returning unsinged values returns signed values if
        text protocol is used. The reason is that the stored proceedure item
        Item_func_sp wasn't initializing the member variables properly based
        on the information contained in the associated result field.
      - The patch is to upon field-item association, ::fix_fields, initialize
        the member variables in appropriate order.
      - Field type of an Item_func_sp was hard coded to MYSQL_TYPE_VARCHAR.
        This is changed to return the type of the actual result field.
      - Member function name sp_result_field was refactored to the more 
        appropriate init_result_field.
      - Member function name find_and_check_access was refactored to 
        sp_check_access.
      
      
      mysql-test/r/sp.result:
        - Added test
      mysql-test/t/sp.test:
        - Added test
      sql/item_func.cc:
        Bug#20777 Function w BIGINT UNSIGNED shows diff. behaviour with and without --ps-protocol
        
        - Stored procedures returning unsinged values returns signed values if
          text protocol is used. The reason is that the stored proceedure item
          Item_func_sp wasn't initializing the member variables properly based
          on the information contained in the associated result field.
        - The patch is to upon field-item association, ::fix_fields, initialize
          the member variables in appropriate order.
        - Field type of an Item_func_sp was hard coded to MYSQL_TYPE_VARCHAR.
          This is changed to to return the type of the actual result field.
        - Member function name sp_result_field was refactored to the more 
          appropriate init_result_field.
        - Member function name find_and_check_access was refactored to 
          sp_check_access.
      sql/item_func.h:
        Bug#20777 Function w BIGINT UNSIGNED shows diff. behaviour with and without --ps-protocol
        
        - Stored procedures returning unsinged values returns signed values if
          text protocol is used. The reason is that the stored proceedure item
          Item_func_sp wasn't initializing the member variables properly based
          on the information contained in the associated result field.
        - The patch is to upon field-item association, ::fix_fields, initialize
          the member variables in appropriate order.
        - Field type of an Item_func_sp was hard coded to MYSQL_TYPE_VARCHAR.
          This is changed to to return the type of the actual result field.
        - Member function name sp_result_field was refactored to the more 
          appropriate init_result_field.
        - Member function name find_and_check_access was refactored to 
          sp_check_access.
      ffc605aa
    • unknown's avatar
      Merge gkodinov@bk-internal.mysql.com:/home/bk/mysql-5.0-opt · 43b9ff1b
      unknown authored
      into  magare.gmz:/home/kgeorge/mysql/autopush/B26261-5.0-opt
      
      
      sql/mysql_priv.h:
        Auto merged
      sql/sql_insert.cc:
        Auto merged
      sql/sql_prepare.cc:
        Auto merged
      mysql-test/r/insert_update.result:
        SCCS merged
      mysql-test/t/insert_update.test:
        SCCS merged
      43b9ff1b
    • unknown's avatar
      Bug #26261: · 2e8e78a4
      unknown authored
       INSERT uses query_id to verify what fields are
       mentioned in the fields list of the INSERT command.
       However the check for that is made after the 
       ON DUPLICATE KEY is processed. This causes all
       the fields mentioned in ON DUPLICATE KEY to be 
       considered as mentioned in the fields list of 
       INSERT.
       Moved the check up, right after processing the
       fields list.
      
      
      mysql-test/r/insert_update.result:
        Bug #26261: test case
      mysql-test/t/insert_update.test:
        Bug #26261: test case
      sql/mysql_priv.h:
        Bug #26261: moved the check inside mysql_prepare_insert
      sql/sql_insert.cc:
        Bug #26261: move the check inside mysql_prepare_insert
        before setting up the ON DUPLICATE KEY part
      sql/sql_prepare.cc:
        Bug #26261: moved the check inside mysql_prepare_insert
      2e8e78a4
    • unknown's avatar
      Merge sgluhov@bk-internal.mysql.com:/home/bk/mysql-5.0-opt · 1a259b88
      unknown authored
      into  mysql.com:/home/gluh/MySQL/Merge/5.0-opt
      
      
      1a259b88
    • unknown's avatar
      Bug#26285 selecting information_schema crahes server · a51b7686
      unknown authored
      The crash happens when 'skip-grant-tables' is enabled.
      We skip the filling of I_S privilege tables 
      if acl_cache is not initialized.
      
      
      mysql-test/r/skip_grants.result:
        test result
      mysql-test/t/skip_grants.test:
        test case
      sql/sql_acl.cc:
        skip filling of I_S privilege tables
        if acl_cache is not initialized
      a51b7686
    • unknown's avatar
      Merge bk@192.168.21.1:mysql-5.0-opt · 6b428e85
      unknown authored
      into  mysql.com:/home/hf/work/mrg/mysql-5.0-opt
      
      
      6b428e85
    • unknown's avatar
      Merge bk@192.168.21.1:mysql-5.0 · 173dc70d
      unknown authored
      into  mysql.com:/home/hf/work/mrg/mysql-5.0-opt
      
      
      sql/sql_parse.cc:
        Auto merged
      173dc70d
  5. 15 Mar, 2007 11 commits
    • unknown's avatar
      Raise version number after cloning 5.0.38 · 0d31e0f3
      unknown authored
      0d31e0f3
    • unknown's avatar
      Merge mysql.com:/home/svoj/devel/bk/mysql-4.1-engines · 19ab799d
      unknown authored
      into  mysql.com:/home/svoj/devel/bk/mysql-5.0-engines
      
      
      19ab799d
    • unknown's avatar
      Merge epotemkin@bk-internal.mysql.com:/home/bk/mysql-5.0-opt · c6ab94bd
      unknown authored
      into  moonbone.local:/mnt/gentoo64/work/27033-bug-5.0-opt-mysql
      
      
      c6ab94bd
    • unknown's avatar
      Bug#27033: 0 as LAST_INSERT_ID() after INSERT .. ON DUPLICATE if rows were · 542f18a3
      unknown authored
      touched but not actually changed.
      
      The LAST_INSERT_ID() is reset to 0 if no rows were inserted or changed.
      This is the case when an INSERT ... ON DUPLICATE KEY UPDATE updates a row
      with the same values as the row contains.
      
      Now the LAST_INSERT_ID() values is reset to 0 only if there were no rows
      successfully inserted or touched.
      The new 'touched' field is added to the COPY_INFO structure. It holds the
      number of rows that were touched no matter whether they were actually
      changed or not.
      
      
      sql/sql_class.h:
        Bug#27033: 0 as LAST_INSERT_ID() after INSERT .. ON DUPLICATE if rows were
        touched but not actually changed.
        
        The new 'touched' field is added to the COPY_INFO structure. It holds the
        number of rows that were touched no matter whether they were actually
        changed or not.
      mysql-test/r/insert_update.result:
        Added a test case for the bug#27033: 0 as LAST_INSERT_ID() after INSERT .. ON DUPLICATE if rows were
        touched but not actually changed.
      mysql-test/t/insert_update.test:
        Added a test case for the bug#27033: 0 as LAST_INSERT_ID() after INSERT .. ON DUPLICATE if rows were
        touched but not actually changed.
      sql/sql_insert.cc:
        Bug#27033: 0 as LAST_INSERT_ID() after INSERT .. ON DUPLICATE if rows were
        touched but not actually changed.
        
        Now the LAST_INSERT_ID() values is reset to 0 only if there were no rows
        successfully inserted or touched.
      542f18a3
    • unknown's avatar
      Merge mysql.com:/home/hf/work/26833/my50-26833 · 34c55867
      unknown authored
      into  mysql.com:/home/hf/work/mrg/mysql-5.0-opt
      
      
      sql/sql_parse.cc:
        Auto merged
      34c55867
    • unknown's avatar
      Merge bk@192.168.21.1:mysql-5.0 · b6515184
      unknown authored
      into  mysql.com:/home/hf/work/mrg/mysql-5.0-opt
      
      
      mysql-test/r/gis-rtree.result:
        Auto merged
      b6515184
    • unknown's avatar
      Merge bk-internal.mysql.com:/home/bk/mysql-4.1 · 39333ba7
      unknown authored
      into  mockturtle.local:/home/dlenev/src/mysql-4.1-merge
      
      
      39333ba7
    • unknown's avatar
      Merge bk-internal.mysql.com:/home/bk/mysql-5.0 · 6f47415f
      unknown authored
      into  mockturtle.local:/home/dlenev/src/mysql-5.0-merge
      
      
      6f47415f
    • unknown's avatar
      Merge mockturtle.local:/home/dlenev/src/mysql-4.1-bg25966 · 04e727c7
      unknown authored
      into  mockturtle.local:/home/dlenev/src/mysql-5.0-bg25966-2
      
      
      sql/mysqld.cc:
        Auto merged
      04e727c7
    • unknown's avatar
      Fix for bug #25966 "2MB per second endless memory consumption after LOCK · cdd2a2e4
      unknown authored
      TABLE ... WRITE".
      
      Memory and CPU hogging occured when connection which had to wait for table
      lock was serviced by thread which previously serviced connection that was
      killed (note that connections can reuse threads if thread cache is enabled).
      One possible scenario which exposed this problem was when thread which
      provided binlog dump to replication slave was implicitly/automatically
      killed when the same slave reconnected and started pulling data through
      different thread/connection.
      The problem also occured when one killed particular query in connection
      (using KILL QUERY) and later this connection had to wait for some table
      lock.
      
      This problem was caused by the fact that thread-specific mysys_var::abort
      variable, which indicates that waiting operations on mysys layer should
      be aborted (this includes waiting for table locks), was set by kill
      operation but was never reset back. So this value was "inherited" by the
      following statements or even other connections (which reused the same
      physical thread). Such discrepancy between this variable and THD::killed
      flag broke logic on SQL-layer and caused CPU and memory hogging.
      
      This patch tries to fix this problem by properly resetting this member.
      
      There is no test-case associated with this patch since it is hard to test
      for memory/CPU hogging conditions in our test-suite.
      
      
      sql/mysqld.cc:
        We should not forget to reset THD::mysys_var::abort after kill operation
        if we are going to use thread to which this operation was applied for
        handling of other connections.
      sql/sp_head.cc:
        We should not forget to reset THD::mysys_var::abort after kill operation
        if we are going to use thread to which this operation was applied for
        handling of further statements.
      sql/sql_parse.cc:
        We should not forget to reset THD::mysys_var::abort after kill operation
        if we are going to use thread to which this operation was applied for
        handling of further statements.
      cdd2a2e4
    • unknown's avatar
      Fix for bug #25966 "2MB per second endless memory consumption after LOCK · db1d2f64
      unknown authored
      TABLE ... WRITE".
      
      CPU hogging occured when connection which had to wait for table lock was
      serviced by thread which previously serviced connection that was killed
      (note that connections can reuse threads if thread cache is enabled).
      One possible scenario which exposed this problem was when thread which
      provided binlog dump to replication slave was implicitly/automatically
      killed when the same slave reconnected and started pulling data through
      different thread/connection.
      In 5.* versions memory hogging was added to CPU hogging. Moreover in
      those versions the problem also occured when one killed particular query
      in connection (using KILL QUERY) and later this connection had to wait for
      some table lock.
      
      This problem was caused by the fact that thread-specific mysys_var::abort
      variable, which indicates that waiting operations on mysys layer should
      be aborted (this includes waiting for table locks), was set by kill
      operation but was never reset back. So this value was "inherited" by the
      following statements or even other connections (which reused the same
      physical thread). Such discrepancy between this variable and THD::killed
      flag broke logic on SQL-layer and caused CPU and memory hogging.
      
      This patch tries to fix this problem by properly resetting this member.
      
      There is no test-case associated with this patch since it is hard to test
      for memory/CPU hogging conditions in our test-suite.
      
      
      sql/mysqld.cc:
        We should not forget to reset THD::mysys_var::abort after kill operation
        if we are going to use thread to which this operation was applied for
        handling of other connections.
      db1d2f64
  6. 14 Mar, 2007 13 commits
    • unknown's avatar
      Merge malff@bk-internal.mysql.com:/home/bk/mysql-5.0-runtime · cfcd27b3
      unknown authored
      into  weblab.(none):/home/marcsql/TREE/mysql-5.0-26503
      
      
      cfcd27b3
    • unknown's avatar
      Bug#26503 (Illegal SQL exception handler code causes the server to crash) · 79344c7b
      unknown authored
      Before this fix, the parser would accept illegal code in SQL exceptions
      handlers, that later causes the runtime to crash when executing the code,
      due to memory violations in the exception handler stack.
      
      The root cause of the problem is instructions within an exception handler
      that jumps to code located outside of the handler. This is illegal according
      to the SQL 2003 standard, since labels located outside the handler are not
      supposed to be visible (they are "out of scope"), so any instruction that
      jumps to these labels, like ITERATE or LEAVE, should not parse.
      
      The section of the standard that is relevant for this is :
        SQL:2003 SQL/PSM (ISO/IEC 9075-4:2003)
        section 13.1 <compound statement>,
        syntax rule 4
      <quote>
        The scope of the <beginning label> is CS excluding every <SQL schema
        statement> contained in CS and excluding every
        <local handler declaration list> contained in CS. <beginning label> shall
        not be equivalent to any other <beginning label>s within that scope.
      </quote>
      
      With this fix, the C++ class sp_pcontext, which represent the "parsing
      context" tree (a.k.a symbol table) of a stored procedure, has been changed
      as follows:
      - constructors have been cleaned up, so that only building a root node for
      the tree is public; building nodes inside a tree is not public.
      - a new member, m_label_scope, indicates if a given syntactic context
      belongs to a DECLARE HANDLER block,
      - label resolution, in the method find_label(), has been changed to
      implement the restriction of scope regarding labels used in a compound
      statement.
      
      The actions in the parser, when parsing the body of a SQL exception handler,
      have been changed as follows:
      - the implementation of an exception handler (DECLARE HANDLER) now creates
      explicitly a new sp_pcontext, to isolate the code inside the handler from
      the containing compound statement context.
      - registering exception handlers as a result occurs in the parent context,
      see the rule sp_hcond_element
      - the code in sp_hcond_list has been cleaned up, to avoid code duplication
      
      In addition, the flags IN_SIMPLE_CASE and IN_HANDLER, declared in sp_head.h
      have been removed, since they are unused and broken by design (as seen with
      Bug 19194 (Right recursion in parser for CASE causes excessive stack usage,
      limitation), representing a stack in a single flag is not possible.
      
      Tests in sp-error have been added to show that illegal constructs are now
      rejected.
      
      Tests in sp have been added for code coverage, to show that ITERATE or LEAVE
      statements are legal when jumping to a label in scope, inside the body of
      an exception handler.
      
      
      mysql-test/r/sp-error.result:
        SQL Exception handlers define a parsing context for label resolution.
      mysql-test/r/sp.result:
        SQL Exception handlers define a parsing context for label resolution.
      mysql-test/t/sp-error.test:
        SQL Exception handlers define a parsing context for label resolution.
      mysql-test/t/sp.test:
        SQL Exception handlers define a parsing context for label resolution.
      sql/sp_head.cc:
        Minor cleanup
      sql/sp_head.h:
        Minor cleanup
      sql/sp_pcontext.cc:
        SQL Exception handlers define a parsing context for label resolution.
      sql/sp_pcontext.h:
        SQL Exception handlers define a parsing context for label resolution.
      sql/sql_yacc.yy:
        SQL Exception handlers define a parsing context for label resolution.
      79344c7b
    • unknown's avatar
      Merge mysql.com:/home/kent/bk/tmp/mysql-4.1-build · 26a7c7ed
      unknown authored
      into  mysql.com:/home/kent/bk/tmp/mysql-5.0-build
      
      
      26a7c7ed
    • unknown's avatar
      Merge mysql.com:/home/kent/bk/tmp/mysql-4.0 · eddf23e0
      unknown authored
      into  mysql.com:/home/kent/bk/tmp/mysql-4.1-build
      
      
      eddf23e0
    • unknown's avatar
      EXCEPTIONS-CLIENT: · 377853e2
      unknown authored
        Updated to version 0.6 of the text
      
      
      EXCEPTIONS-CLIENT:
        Updated to version 0.6 of the text
      377853e2
    • unknown's avatar
      Bug #26794: fixed valgrind warning · ff810fb9
      unknown authored
      ff810fb9
    • unknown's avatar
      Merge mysql.com:/home/kent/bk/tmp/mysql-4.1-build · 29e6d308
      unknown authored
      into  mysql.com:/home/kent/bk/tmp/mysql-5.0-build
      
      
      configure.in:
        Auto merged
      29e6d308
    • unknown's avatar
      Merge kboortz@bk-internal.mysql.com:/home/bk/mysql-5.0 · 1c02d8c0
      unknown authored
      into  mysql.com:/home/kent/bk/tmp/mysql-5.0-build
      
      
      1c02d8c0
    • unknown's avatar
      Merge kboortz@bk-internal.mysql.com:/home/bk/mysql-4.1 · f4656c37
      unknown authored
      into  mysql.com:/home/kent/bk/tmp/mysql-4.1-build
      
      
      f4656c37
    • unknown's avatar
      Merge mysql.com:/home/kent/bk/tmp/mysql-4.0 · 9be5d518
      unknown authored
      into  mysql.com:/home/kent/bk/tmp/mysql-4.1-build
      
      
      configure.in:
        SCCS merged
      9be5d518
    • unknown's avatar
      configure.in: · 0f7f7ff8
      unknown authored
        Added test for sched_yield() possibly in -lposix4 on Solaris
      
      
      configure.in:
        Added test for sched_yield() possibly in -lposix4 on Solaris
      0f7f7ff8
    • unknown's avatar
      Merge gkodinov@bk-internal.mysql.com:/home/bk/mysql-5.0-opt · 347e832a
      unknown authored
      into  magare.gmz:/home/kgeorge/mysql/autopush/B26794-5.0-opt
      
      
      sql/field.cc:
        Auto merged
      347e832a
    • unknown's avatar
      Bug #26794: · a22f257e
      unknown authored
      Different set of conditions is used to verify
      the validity of index definitions over a GEOMETRY
      column in ALTER TABLE and CREATE TABLE. 
      The difference was on how sub-keys notion validity
      is checked.
      Fixed by extending the CREATE TABLE condition to
      support the cases allowed in ALTER TABLE.
      Made the SHOW CREATE TABLE not to display spatial
      indexes using the sub-key notion.
      
      
      mysql-test/r/alter_table.result:
        Bug #26794: test case
      mysql-test/r/gis-rtree.result:
        Bug #26794: fixed SHOW CREATE TABLE output.
      mysql-test/t/alter_table.test:
        Bug #26794: test case
      sql/field.cc:
        Bug #26794: Allow sub-keys for GEOMETRY
      sql/sql_show.cc:
        Bug #26794: Don't show sub-key notion 
         in SHOW CREATE TABLE for SPATIAL indexes.
      sql/sql_table.cc:
        Bug #26794: Allow sub-keys for GEOMETRY
      a22f257e
  7. 13 Mar, 2007 4 commits
    • unknown's avatar
      Removed tabs. · 8205e16c
      unknown authored
      8205e16c
    • unknown's avatar
      Merge gkodinov@bk-internal.mysql.com:/home/bk/mysql-5.0-opt · 4108ca96
      unknown authored
      into  magare.gmz:/home/kgeorge/mysql/autopush/B26672-5.0-opt
      
      
      mysql-test/r/order_by.result:
        Auto merged
      mysql-test/t/order_by.test:
        Auto merged
      4108ca96
    • unknown's avatar
      Merge mysql.com:/home/svoj/devel/mysql/BUG26881/mysql-4.1-engines · 968d1695
      unknown authored
      into  mysql.com:/home/svoj/devel/mysql/BUG26881/mysql-5.0-engines
      
      
      myisam/mi_create.c:
        Auto merged
      mysql-test/t/merge.test:
        Auto merged
      sql/ha_myisam.cc:
        Auto merged
      sql/sql_parse.cc:
        Use local.
      mysql-test/r/merge.result:
        SCCS merged
      968d1695
    • unknown's avatar
      BUG#26881 - Large MERGE tables report incorrect specification when no · 969b7165
      unknown authored
                  differences in tables
      Certain merge tables were wrongly reported as having incorrect definition:
      - Some fields that are 1 byte long (e.g. TINYINT, CHAR(1)), might
        be internally casted (in certain cases) to a different type on a
        storage engine layer. (affects 4.1 and up)
      - If tables in a merge (and a MERGE table itself) had short VARCHAR column (less
        than 4 bytes) and at least one (but not all) tables were ALTER'ed (even to an
        identical table: ALTER TABLE xxx ENGINE=yyy), table definitions went ouf of
        sync. (affects 4.1 only)
      
      This is fixed by relaxing a check for underlying conformance and setting
      field type to FIELD_TYPE_STRING in case varchar is shorter than 4
      when a table is created.
      
      
      myisam/mi_create.c:
        Added a comment.
      mysql-test/r/merge.result:
        A test case for bug#26881.
      mysql-test/t/merge.test:
        A test case for bug#26881.
      sql/ha_myisam.cc:
        Relaxed some checks performed by check_definition():
        As comparing of fulltext keys (and key segments) is not yet implemented,
        only return an error in case one of keys is fulltext and other is not.
        Otherwise, if both keys are fulltext, accept them as is.
        
        As comparing of spatial keys (and key segments) is not yet implemented,
        only return an error in case one of keys is spatial and other is not.
        Otherwise, if both keys are spatial, accept them as is.
        
        A workaround to handle situation when field is casted from FIELD_SKIP_ZERO
        to FIELD_NORMAL. This could happen only in case field length is 1 and row
        format is fixed.
      sql/sql_parse.cc:
        When a table that has varchar field shorter than 4 is created, field type is
        set to FIELD_TYPE_VAR_STRING. Later, when a table is modified using alter
        table, field type is changed to FIELD_TYPE_STRING (see Field_string::type).
        That means HA_OPTION_PACK_RECORD flag might be lost and thus null_bit might
        be shifted by alter table, in other words alter table doesn't create 100%
        equal table definition.
        
        This is usually not a problem, since when a table is created/altered,
        definition on a storage engine layer is based on one that is passed from
        sql layer. But it is a problem for merge engine - null_bit is shifted when
        a table (merge or underlying) is altered.
        
        Set field type to FIELD_TYPE_STRING in case FIELD_TYPE_VAR_STRING is shorter
        than 4 when a table is created as it is done in Field::type.
      969b7165