expression index not used within function

Hi,

I have created an index as follows:

(replace(lower(my_column), ' '::text, ''::text)

which i use in a WHERE clause against LIKE 'string%'

By using text_pattern_ops i get the index used provided i more than one
character is used in the string.

However, with the same SELECT query running within a function (using RETURNS
TABLE) the query takes significantly longer - as though the index is
ignored. e.g. 2500ms instead of 12ms

Is there something fundamental i'm missing about the use of the indexed
expression?

Thanks!

Andy

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