Karl Denninger wrote:
The bitmask allows the setting of multiple permissions but the table
definition doesn't have to change (well, so long as the bits fit into a
word!) Finally, this is a message forum - the actual code itself is
template-driven and the bitmask permission structure is ALL OVER the
templates; getting that out of there would be a really nasty rewrite,
not to mention breaking the user (non-developer, but owner)
extensibility of the current structure.
Is there a way to TELL the planner how to deal with this, even if it
makes the SQL non-portable or is a hack on the source mandatory?
You could maybe create function indexes for common bitmap operations;
for example if it's common to check a single bit you could create 32
indexes, on (field & 1), (field & 2), (field & 4), etc. You could also
maybe extend this so if you need to query multiple bits you decompose
them into individual single-bit queries, e.g. instead of (field & 3) you
do ((field & 1) and (field & 2)).
I suppose there will be a break-even point in complexity before which
the above approach will be very slow but after it it should scale better
then the alternative.
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