Mark Kirkwood <[EMAIL PROTECTED]> writes: > An obvious deduction is that the TPCH dataset is much more amenable to > run compression than my synthetic Zipfian data was. The interesting > question is how well "real" datasets are run compressable,
Yeah --- the back-of-the-envelope calculations I was making presupposed uniform random distribution, and we know that's often not realistic for real datasets. A nonuniform distribution would probably mean that some of the bitmaps compress better-than-expected and others worse. I have no idea how to model that and guess what the overall result is ... regards, tom lane ---------------------------(end of broadcast)--------------------------- 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 match