Tom Lane <[EMAIL PROTECTED]> writes:

> No, what you'll get is something like
>       int4var::float8 float8eq float8var
> which is perfectly mergejoinable ... however, it's not clear that the
> planner will make very good estimates about the value of the cast
> expression.  I'm not sure if it's worth introducing a pile more
> crosstype operators to change that situation --- improving
> the selectivity functions to handle casts better might be a wiser
> approach.

So the only reason we needed the cross-data-type operators was to get better
estimates? I thought without them you couldn't get an index-based plan at all.

  Gregory Stark

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TIP 9: In versions below 8.0, the planner will ignore your desire to
       choose an index scan if your joining column's datatypes do not

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