Re: creating an index on a function

[2002-02-15 09:26] Nick Fankhauser said:
| Good Morning everyone!
|
| I just tried to create an index on a function with no success. My syntax
| seems to match the syntax shown in the docs for Create Index, but I get an
| error. Any thoughts would be appreciated. Here is my attempt-
|
| First, I did a select to make sure I had the function syntax correct, and
| then tried to create the index:
|
|
| staging=# select count(*) from event where
| date_trunc('day',event_date_time)='07/27/2001';
| count
| -------
| 27
| (1 row)
|
| staging=#
| staging=# create index event_day on
| event(date_trunc('day',event_date_time));

You cannot create an index on a function with constant parameters.
This limitation may be removed in a future version, but for now
you have to create a wrapper function that doesn't require the
constant parameter

CREATE FUNCTION date_trunc_day(TIMESTAMP) RETURNS TIMESTAMP AS '
SELECT date_trunc(''day'',$1);
' LANGUAGE 'sql';

then use this to create your function index.

create index event_day on
event(date_trunc_day(event_date_time));

hth.
brent

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