FreeTDS Development Group

["James K. Lowden" <jklowden AT schemamania.org>]

I spent quite a bit of the weekend going over bcp.c tracking down
UTF-8 issues.  I noticed that BCP_COLINFO functionally duplicates
TDSCOLINFO, making the code harder (for me at least) to understand. 
More important, as TDSCOLINFO info changes to support iconv, those
same changes are going to have to be re-invented in BCP_COLINFO.  

It would be nice IMO if someone had the time to rip out BCP_COLINFO
and replace it with TDSCOLINFO.  If nothing else, I'll do that when I
migrate bcp.c from db-lib to libtds, in preparation for blk-lib use.
(I also think the "column_" prefix should go.)   

Here's my analysis of the two structures.  

BCP_COLINFO     TDSCOLINFO      
tab_colnum
db_type         column_type
db_length       column_size
db_nullable     column_nullable
data            column_offset   // semantically different
data_size       column_cur_size
db_usertype     column_usertype
db_flags        column_flags
db_type_save    on_server.column_type
db_prec         column_prec
db_scale        column_scale
db_collate      column_collation
db_name         column_name
db_varint_size  column_varint_size

db_name         column_name
db_minlen       // not used     
db_maxlen       // not used     
db_colcnt       // not used     
db_status       // not used     
db_offset       // not used
db_default      // not used     
db_size         // not used     
txptr_offset    column_textpos

As you can see, BCP_COLINFO has many fields not in TDSCOLINFO, but
only one of these is used.  

I also noticed that DBPROCESS::bcp_columns is an array of pointers to
BCP_COLINFO structures.  It turns out, however, that we always know
how many columns there are, so we could allocate an array of structs
directly, gaining some efficiency and losing one level of
indirection.  
        
For completeness, here are the TDSCOLINFO members not represented in
BCP_COLINFO:  

column_namelen
table_namelen
on_server.column_size
table_name
column_writeable
column_identity
column_output
column_operator
column_operand
column_bindtype
column_bindfmt
column_bindlen
column_nullbind
column_varaddr
column_lenbind
column_text_sqlgetdatapos

--jkl