Hey Jim!


>>The speculation about the bit-mapping doesn't seem to make allowances for B-Tree functionality. Surely that has to play some important role in all of this.
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The b-tree would only apply during a seek operation.

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Similarly, speculation about the bit-mapping implies (to me, as I have read this thread) that the whole index would necessarily be read into RAM. I have to wonder about this too.

Finally, and this may be what Dragan was saying, even if the whole index *is* read in, the order should be immaterial for bit-map *building* purposes, since the record number is supplied with each index entry (thus providing the offset for the bit in question anyway).
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Actually the bitmap is built based on the index tags. That precludes keeping the entire index tag in RAM which could become very difficult. Assuming a 4 byte record number and a single bit for the condition, you'd need 5 bits per record.

A single bit per record would require 1/5th the storage in RAM. However, the bitmap could not be built in anything other than record # order if its only 1 bit per record.