[mdb-dev] Re: mdb-schema field size

[Alfred A. <al...@an...>]

The text sizes in different versions of Access are different (8-bit 
characters vs. 16-bit characters)
and MDB reports the *actual*sizes okay. How to interpret them when 
creating the database description
is a different thing. I solved this problem by dividing it by two if Jet 
version is 4 here is a code snippet:

/*
 * col_size contains column size;
 * if it comes from JET4 database, divide it by two
 * otherwise kep it as is, for it might be okay :-?
 */

if (IS_JET4(mdb))
    col_size /= 2;

>Date: Sun, 09 Oct 2005 15:22:05 -0600
>To: mdb...@li...
>From: "Michael D. Petersen" <ra...@dr...>
>Subject: [mdb-dev] mdb-schema field size
>
>I am using mdb-schema to export an Access 2000 database.  All is working 
>well expect the field sizes of the text fields are all twice as large as 
>they should be in the mdb-schema output.  For example, I have two text 
>fields, one length 5 and the other 255 as reported by Access.  However, the 
>schema output (mysql backend) is:
>
>DROP TABLE Table1;
>CREATE TABLE Table1
>  (
>         TextField5                      varchar (10),
>         TextField255                    varchar (510)
>);
>
>The content of the test file is (mdb-export):
>TextField5,TextField255
>"abcde","LotsOfData"
>
>Is this a bug?  A character set issue?  Is there a work-around already 
>designed into mdbtools?  The problem is that MySQL doesn't like the varchar 
>fields being larger than 255 (it wants a BLOB instead) when importing the 
>schema file.  Also, it allocates twice the size than necessary.  When 
>viewing the .mdb file with a hex editor all the field contents are contiguous:
>
>    1afe0  00 00 02 00 ff fe 61 62  63 64 65 ff fe 4c 6f 74  ......abcde..Lot
>    1aff0  73 4f 66 44 61 74 61 15  00 09 00 02 00 02 00 03  sOfData.........
>
>Therefore, there doesn't seem to be a reason why the size should come up 
>double what Access says it is, unless I'm misunderstanding something here 
>(entirely possible...).
>
>I have recreated this problem using a very simple Access database generated 
>from scratch (above).  I have also tried using mdbtools compiled on 
>Cygwin(Win2k) and Linux, both from the CVS sources, with the same 
>results.  The field sizes are also independent of the backend selected in 
>mdb-schema.
>
>Thanks for the help,
>Michael
>  
>