From: Jeff Hostetler Date: Thu, 27 Jun 2019 13:24:46 GMT Subject: Re: [PATCH v2 05/10] split-index.c: dump "link" extension as json Message-ID: <93562f66-07a7-d074-e225-65afd7ced1d4@jeffhostetler.com> In-Reply-To: On 6/27/2019 6:48 AM, Duy Nguyen wrote: > On Tue, Jun 25, 2019 at 7:40 PM Derrick Stolee wrote: >> >> On 6/25/2019 6:29 AM, Duy Nguyen wrote: >>> On Tue, Jun 25, 2019 at 3:06 AM Jeff Hostetler wrote: >>>> I'm curious how big these EWAHs will be in practice and >>>> how useful an array of integers will be (especially as the >>>> pretty format will be one integer per line). Perhaps it >>>> would helpful to have an extended example in one of the >>>> tests. >>> >>> It's one integer per updated entry. So if you have a giant index and >>> updated every single one of them, the EWAH bitmap contains that many >>> integers. >>> >>> If it was easy to just merge these bitmaps back to the entry (e.g. in >>> this example, add "replaced": true to entry zero) I would have done >>> it. But we dump as we stream and it's already too late to do it. >>> >>>> Would it be better to have the caller of ewah_each_bit() >>>> build a hex or bit string in a strbuf and then write it >>>> as a single string? >>> >>> I don't think the current EWAH representation is easy to read in the >>> first place. You'll probably have to run through some script to update >>> the main entries part and will have a much better view, but that's >>> pretty quick. If it's for scripts, then it's probably best to keep as >>> an array of integers, not a string. Less post processing. >> >> I don't think the intent is to dump the EWAH directly, but instead to >> dump a string of the uncompressed bitmap. Something like: >> >> "delete_bitmap" : "01101101101" >> >> instead of >> >> "delete_bitmap" : [ 0, 1, 1, 0, 1, 1, 0, 1, 1, 1, 0, 1 ] > > I get this part. But the numbers in the array were the position of the > set bits. It's not showing just the actual bit map. > > The same bitmap would be currently displayed as > > "delete_bitmap": [ 1, 2, 4, 5, 7, 8, 9, 11 ] > > And that maps back to the entry[1], entry[2], entry[4]... in the index > being deleted from the base index. So displaying as a real bit map > actually adds more work for both the reader and the tool because you > have to calculate the position either way. And it gets harder if the > bit you're intereted in is on the far right. Thanks for the clarification. That helps. Jeff