Consistent method of inserting TEXT column to Informix database using JDBC and ODBC

Question

I have problem when I try insert some data to Informix TEXT column via JDBC. In ODBC I can simply run SQL like this:

INSERT INTO test_table (text_column) VAL         


        

Answer 1

First off, are you really sure you want to use an Informix TEXT type? The type is a nuisance to use, in part because of the problems you are facing. It pre-dates anything in any SQL standard with respect to large objects (TEXT still isn't in SQL-2003 - though approximately equivalent structures, CLOB and BLOB, are). And the functionality of BYTE and TEXT blobs has not been changed since - oh, let's say 1996, though I suspect there's a case for choosing an earlier date, like 1991.

In particular, how much data are you planning to store in the TEXT columns? Your example shows the string 'insert'; that is, I presume, much much smaller than you would really use. You should be aware that a BYTE or TEXT columns uses a 56-byte descriptor in the table plus a separate page (or set of pages) to store the actual data. So, for tiny strings like that, it is a waste of space and bandwidth (because the data for the BYTE or TEXT objects will be shipped between client and server separately from the rest of the row). If your size won't get above about 32 KB, then you should look at using LVARCHAR instead of TEXT. If you will be using data sizes above that, then BYTE or TEXT or BLOB or CLOB are sensible alternatives, but you should look at configuring either blob spaces (for BYTE or TEXT) or smart blob spaces (for BLOB or CLOB). You can, and are, using TEXT IN TABLE, rather than in a blob space; be aware that doing so impacts your logical logs whereas using a blob space does not impact them anything like as much.

One of the features I've been campaigning for a decade or so is the ability to pass string literals in SQL statements as TEXT literals (or BYTE literals). That is in part because of the experience of people like you. I haven't yet been successful in getting it prioritized ahead of other changes that need to be made. Of course, you need to be aware that the maximum size of an SQL statement is 64 KB text, so you could create too big an SQL statement if you aren't careful; placeholders (question marks) in the SQL normally prevent that being a problem - and increasing the size of an SQL statement is another feature request which I've been campaigning for, but a little less ardently.

OK, assuming that you have sound reasons for using TEXT...what next. I'm not clear what Java (the JDBC driver) is doing behind the scenes - apart from too much - but it is a fair bet that it is noticing that a TEXT 'locator' structure is needed and is shipping the parameter in the correct format. It appears that the ODBC driver is not indulging you with similar shenanigans.

In ESQL/C, where I normally work, then the code has to deal with BYTE and TEXT differently from everything else (and BLOB and CLOB have to be dealt with differently again). But you can create and populate a locator structure (loc_t or ifx_loc_t from locator.h - which may not be in the ODBC directory; it is in $INFORMIXDIR/incl/esql by default) and pass that to the ESQL/C code as the host variable for the relevant placeholder in the SQL statement. In principle, there is probably a parallel method available for ODBC. You may have to look at the Informix ODBC driver manual to find it, though.