Padraig O'Sullivan wrote:
Hi,
I'm sure this question has been asked a million times before but I
wanted to ask it as I'm unfamiliar with this code base and its
history.
There is no such thing as a silly question. :)
For a class I'm taking, I've been reading the paper 'Join Processing
in Database Systems with Large Main Memories' by Shapiro which talks
about how great hash joins are. I was just wondering if there is a
reason why hash joins are not implemented in Drizzle? I would have
thought that hash joins might be beneficial in the environments that
Drizzle is targeting - those with large amounts of memory.
Some of the reasons that I was thinking of for no implementation of
hash joins are (feel free to correct me, that is the reason I'm
sending this email):
- deliberate design choice to leave them out
- difficulty of implementing them with the current code case
Despite Brian's previous response I think ^^ is the main reason.
Frankly, changing anything in the runtime and optimizer is like walking
on eggshells.
I think the endeavour is a worthy one, but I will go ahead and warn you
that this is > 1 semester project ;)
Cheers!
jay
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