[HACKERS] How to pass around collation information
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From: Peter Eisentraut on 28 May 2010 12:27 I have been thinking about this collation support business a bit. Ignoring for the moment where we would get the actual collation routines from, I wonder how we are going to pass this information around in the system. Someone declares a collation on a column in a table, and somehow this information needs to arrive in bttextcmp() and friends. Also, functions that take in a string and return one (e.g., substring), need to take in this information and return it back out. How should this work? Option 1, make it part of the datum. That way it will pass through the system just fine, but it would waste a lot of storage and break just about everything that operates on string types now, as well as pg_upgrade. So that's probably out. Option 2, invent some new mechanism that accompanies a datum or a type whereever it goes. Kind of like typmod, but not really. Then the collation information would presumably be made available to functions through the fmgr interface. The binary representation of data values stays the same. Option 2a, while we are at it, are there any other things of this nature that would be worth supporting at the same time? I could imagine that having the option to pass around the ctype locale or the text search dictionary in a similar way could be useful. Is this something that could be combined with typmod or other dormant data type metadata requirements (PostGIS?, XML?)? Ideas? -- Sent via pgsql-hackers mailing list (pgsql-hackers(a)postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers |