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Shared ispell dictionary (stored in shared segment, used by multiple connections)
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Shared ISpell Dictionary ======================== This PostgreSQL extension provides a shared ispell dictionary, i.e. a dictionary that's stored in shared segment. The traditional ispell implementation means that each session initializes and stores the dictionary on it's own, which means a lot of CPU/RAM is wasted. This extension allocates an area in shared segment (you have to choose the size in advance) and then loads the dictionary into it when it's used for the first time. If you need just snowball-type dictionaries, this extension is not really interesting for you. But if you really need an ispell dictionary, this may save you a lot of resources. Install ------- Installing the extension is quite simple, especially if you're on 9.1. In that case all you need to do is this: $ make install and then (after connecting to the database) db=# CREATE EXTENSION shared_ispell; If you're on pre-9.1 version, you'll have to do the second part manually by running the SQL script (shared_ispell--x.y.sql) in the database. If needed, replace MODULE_PATHNAME by $libdir. Config ------ No the functions are created, but you still need to load the shared module. This needs to be done from postgresql.conf, as the module needs to allocate space in the shared memory segment. So add this to the config file (or update the current values) # libraries to load shared_preload_libraries = 'shared_ispell' # known GUC prefixes custom_variable_classes = 'shared_ispell' # config of the shared memory shared_ispell.max_size = 30MB Yes, there's a single GUC variable that defines the maximum size of the shared segment. This is a hard limit, the shared segment is not extensible and you need to set it so that all the dictionaries fit into it and not much memory is wasted. To find out how much memory you actually need, use a large value (e.g. 200MB) and load all the dictionaries you want to use. Then use the shared_ispell_mem_used() function to find out how much memory was actually used (and set the max_size GUC variable accordingly). Don't set it exactly to that value, leave there some free space, so that you can reload the dictionaries without changing the GUC max_size limit (which requires a restart of the DB). Ssomething like 512kB should be just fine. The shared segment can contain several dictionaries at the same time, the amount of memory is the only limit. There's no limit on number of dictionaries / words etc. Just the max_size GUC variable. Using the dictionary -------------------- Technically, the extension defines a 'shared_ispell' template that you may use to define custom dictionaries. E.g. you may do this CREATE TEXT SEARCH DICTIONARY czech_shared ( TEMPLATE = shared_ispell, DictFile = czech, AffFile = czech, StopWords = czech ); CREATE TEXT SEARCH CONFIGURATION public.czech_shared ( COPY = pg_catalog.simple ); ALTER TEXT SEARCH CONFIGURATION czech_shared ALTER MAPPING FOR asciiword, asciihword, hword_asciipart, word, hword, hword_part WITH czech_shared; and then do the usual stuff, e.g. SELECT ts_lexize('czech_shared', 'automobile'); or whatever you want. Resetting the dictionary ------------------------ If you need to reset the dictionary (e.g. so that you can reload the updated files from disk), use shared_ispell_reset() function. Eveyone who already uses the dictionaries will be forced to reinitialize the data (first one will rebuild the dictionary in shared segment, the other ones will use this). SELECT shared_ispell_reset(); That's all for now ...