Hi everyone, In response to an email last year (see http://archives.postgresql.org/pgsql-hackers/2003-10/msg00113.php for more information), I'm beginning to write a patch for PostgreSQL to enable people to write their own ANALYZE routines for user-defined types. In terms of the PostgreSQL "itch and scratch" philosophy, the main reason to do this is to allow PostGIS to update its geometric histogram as part of the analyze process, instead of having to execute a separate stored procedure on a regular basis. This is information is then used as part of the GiST selectivity function to give PostgreSQL the details needed to make the right decision about indexes.
The basic plan is as follows: to move the existing analysis function out of analyze_rel() and assign it an OID, then assign that OID by default to each type in the pg_types table. Finally analyze_rel() will be modified to call the ANALYZE routine for the given OID in the type table. I've spent a few hours looking over the code but I have some questions that I hope can be answered by members on this list (particularly core team members!): 1) Is the basic plan above thinking along the right lines? 2) Should the statistical data for custom types be stored in the pg_statistic table, or should it be the responsibility of the custom type to store this in separate tables itself? 3) If pg_statistic is the best place to store the data, what would be the most appropriate structure to send/receive from the custom analyze function? It looks as if VacAttrStats would do the job, although I'm not convinced that passing a non-datum/standard C types to a user function is a good idea? And then also what would be appropriate values for the other fields, in particular sta_kind, staopX and stanumbersX? Many thanks, Mark. --- Mark Cave-Ayland Webbased Ltd. Tamar Science Park Derriford Plymouth PL6 8BX England Tel: +44 (0)1752 764445 Fax: +44 (0)1752 764446 This email and any attachments are confidential to the intended recipient and may also be privileged. If you are not the intended recipient please delete it from your system and notify the sender. You should not copy it or use it for any purpose nor disclose or distribute its contents to any other person. ---------------------------(end of broadcast)--------------------------- TIP 4: Don't 'kill -9' the postmaster
