Naz Gassiep <naz@xxxxxxxx> writes:
>> Why are hash indexes "obviously" best? In an ideal world with a good
>> implementation maybe, but postgresql b-trees are really quite good.
>>
> Because doing normal queries on a table where there are large text
> blocks is unlikely to be a good idea. E.g.,:
> SELECT * FROM table WHERE textcol = 'a 4kb block of text';
You seem to be harboring some rather severe conceptual errors about
how hash indexes work, or at least how Postgres' hash indexes work.
I get the impression you think that a hash index stores only a hash
code and not the actual field value, but that's not so.
regards, tom lane
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