Tom Lane wrote:
Heikki Linnakangas <[EMAIL PROTECTED]> writes:
[EMAIL PROTECTED] wrote:
The function convert_to(string text, dest_encoding name) is not allowed to
be used in a index expression, because it is not marked as "IMMUTABLE".
You can change the way a conversion is done with CREATE/DROP CONVERSION.
That's why it can't be IMMUTABLE.
The other reason is that it depends on the database encoding. I suppose
you could make an argument that that's fixed for as long as IMMUTABLE
needs to think about --- but we'd have to remember to undo the marking
if database encoding ever becomes less fixed.
Just out of curiosity, what's the use-case for this function in an index
anyway?
regards, tom lane
Thank you all for the responses!
Well, the use case is a strange one... I would like to use a varchar()
column for storing a variable-length vector of integers. The numbers are
represented by the codepoints. Therefore, I need to sort them as binary
data, not as characters. I would often need to get all the vectors that
lie in between to vectors, therefore I need the "binary" index.
And the code should be as database independent as possible, therefore I
cannot use an array or another data type that may not be supported by
other DBMS.
Regards,
Andreas Peer
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