For "count(*) while index_column = value" an index read
is done. It consists of an index scan and retrieval of
each key.
For efficiency reasons the index scan stores the key in
the special buffer 'lastkey2' once only. At the first
iteration it notes this fact with the flag
HA_STATE_RNEXT_SAME in 'info->update'.
For efficiency reasons, the key retrieval for blobs
does not allocate a new buffer, but uses 'lastkey2'...
Now I clear the HA_STATE_RNEXT_SAME flag whenever the
buffer has been polluted. In this case, the index scan
copies the key value again (and sets the flag again).
NDB cluster is not fully supported. This will be added with
WL 1892 (NDB Handler: Add support for CREATE/DROP INDEX).
Some preparatory code for this is already present though.
A change for the "duplicate key" error message is planned
for another changeset.
Changed my_error() to print error messages, which come from
arbitrary registered ranges of error messages. Messages can
be unregistered (and should be at end of the program).
Added registration of handler error messages.
Added a new mi_print_error() macro and a new
mi_report_error() function, which supply error
messages with a table name.
Added calls to mi_print_error() or mi_report_error()
at all places in MyISAM, where table corruption is detected.
Add support for VARCHAR with 1 or 2 length bytes
Enable VARCHAR packing in MyISAM files (previous patch didn't pack data properly)
Give error if we got problems in temporary tables during a SELECT
Don't use new table generated by ALTER TABLE if index generation fails
Fixed wrong call by range_end() (Could cause an ASSERT in debug mode)
Renamed HA_VAR_LENGTH to HA_VAR_LENGTH_PART
Renamed in all files FIELD_TYPE_STRING and FIELD_TYPE_VAR_STRING to MYSQL_TYPE_STRING and MYSQL_TYPE_VAR_STRING to make it easy to catch all possible errors
Added support for VARCHAR KEYS to heap
Removed support for ISAM
Now only long VARCHAR columns are changed to TEXT on demand (not CHAR)
Internal temporary files can now use fixed length tables if the used VARCHAR columns are short
more logical table/index_flags
return HA_ERR_WRONG_COMMAND instead of abstract methods where appropriate
max_keys and other limits renamed to max_supported_keys/etc
max_keys/etc are now wrappers to max_supported_keys/etc
ha_index_init/ha_rnd_init/ha_index_end/ha_rnd_end are now wrappers to real {index,rnd}_{init,end} to enforce strict pairing
New records_in_range() interface (similar to read_range())
Macros for faster bitmap handling
Simplify read_range() code (#WL1786)
New general key_cmp() function to compare keys
