Hello, > Great! I've been working on array support but never had time to finish > it. >
I checked the HEAD of the repository-trunk, but did not find any evedence for array support. Did you ever commit the work you have done so far? > > If there is any interrest, I would like to publish this workarround on > the > > wiki. Where shall I post this? > > Easiest thing, I think, is to open a bug ticket for it on pqxx.org. > Basically it works like this: (I am afraid, this might by to much a hack for some customers) First I create a pure C function which does nothing else than copying the raw array-data into a Postgres bytea-object. This function must be part of a Postgres shared object, which has to be loaded into the server-side-part of Postgres, ie. SPI-functions. Next in the Postgres-shell you have to load this shared object, register the function with Postgres and create a cast using this function: # CREATE FUNCTION my_cast(int[]) RETURNS bytea AS 'mylib.so', 'my_cast' \ LANGUAGE c IMMUTABLE STRICT; # CREATE CAST(int[] AS bytea) WITH FUNCTION my_cast(int[]); During a pqxx-query, one can ask for the array as std::ostringstream sql; sql<<"SELECT CAST(myarray AS bytea) FROM mytable WHERE 1"; pqxx::result query = cur.exec(sql.str()); (...snip...) not the raw array can be used as pqxx::binarystring bytea(tuple[0]); and by reintrerpret_cast'ing bytea.data() to my special class (which basically only recalculates the offsets), the real integer array can be extracted to an int* This also works for float's and all other fixed-size types. 1. This solution has a big drawback. Since clients and servers can be on different endian'ess hosts, array-data would have to be converted, using function such as htonl and ntohl. In my case I can skip this, because I know that they run on the same hardware. 2. Many clients might not be willing to install a shared module to do the conversion between int[] and bytea. While my solution works fine for me, I am not sure, that this can be a general approach. However, I did not find any other solution to transfer array data, unless one is willing to perform a binary-to-ascii-to-binray-conversion. If there is a better concept, please let me know. If you think my solution is of generic usage, I will work on my conversion-class to make it more pqxx-like. Jacob -- GMX FreeMail: 1 GB Postfach, 5 E-Mail-Adressen, 10 Free SMS. Alle Infos und kostenlose Anmeldung: http://www.gmx.net/de/go/freemail _______________________________________________ Libpqxx-general mailing list Libpqxx-general@gborg.postgresql.org http://gborg.postgresql.org/mailman/listinfo/libpqxx-general
