[PERFORM] Impact of varchar/text in use of indexes

[Mike Moran]

Hi. I have two existing tables, A and B. A has a 'varchar(1000)' field 
and B has a 'text' field, each with btree indexes defined. When I do a 
join between these, on this field, it seems to a hash join, as opposed 
to using the indexes, as I might expect (I'm no postgres expert, btw).

My question is: if I changed both fields to be text or varchar(1000) 
then would the index be used?

Ta,

--
Mike


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Re: [PERFORM] Impact of varchar/text in use of indexes

[Tom Lane]

Mike Moran [EMAIL PROTECTED] writes:
 Hi. I have two existing tables, A and B. A has a 'varchar(1000)' field 
 and B has a 'text' field, each with btree indexes defined. When I do a 
 join between these, on this field, it seems to a hash join, as opposed 
 to using the indexes, as I might expect (I'm no postgres expert, btw).

 My question is: if I changed both fields to be text or varchar(1000) 
 then would the index be used?

Probably not, and in any case your assumption is mistaken.  Indexes are
not always the right way to join.

regards, tom lane

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