1. What is the structure of the Bloom Index ? Can you please let me know what are the fields of a Bloom Index ? Is it just the Item Pointer and BloomSignatureWord ? When i describe my bloom index it looks like following.
2. If we are storing just one signature word per row, how is this aggregated for all column values of that row into one signature in high level ? For example, if length = 64, does it mean that a bit array of 64 bits is generated per each row ?
If col1=4, does it mean the value of col1 is passed to 4 hash functions that generate 4 positions that can be set to 1 in the bit array ?
> I was testing bloom indexes today. I understand bloom indexes uses bloom > filters. [...] > > So the question here is - > I assume - number of bits = k. Where k is the total number of hash > functions used on top of the data that needs to validated. Is that correct > ? If yes, why do we see the Index 1 performing better than Index 2 ? > Because, the data has to go through more hash functions (4 vs 2) in Index 1 > than Index 2. So, with Index 1 it should take more time. > Also, both the indexes have ZERO false positives. > Please let me know if there is anything simple that i am missing here.
You may have a look at the blog entry about these parameters I redacted a few year ago:
