All, So these results have become a bit complex. So spreadsheet time.
https://docs.google.com/spreadsheets/d/1Mokpx3EqlbWlFDIkF9qzpM7NneN9z-QOXWSzws3E-R4 Some details: The Length-and-Offset test was performed using a more recent 9.4 checkout than the other two tests. This was regrettable, and due to a mistake with git, since the results tell me that there have been some other changes. I added two new datasets: errlog2 is a simple, 4-column error log in JSON format, with 2 small values and 2 large values in each datum. It was there to check if any of our changes affected the performance or size of such simple structures (answer: no). processed_b is a synthetic version of Mozilla Socorro's crash dumps, about 900,000 of them, with nearly identical JSON on each row. These are large json values (around 4KB each) with a broad mix of values and 5 levels of nesting. However, none of the levels have very many keys per level; the max is that the top level has up to 40 keys. Unlike the other data sets, I can provide a copy of processed_b for asking. So, some observations: * Data sizes with lengths-and-offets are slightly (3%) larger than all-lengths for the pathological case (jsonbish) and unaffected for other cases. * Even large, complex JSON (processed_b) gets better compression with the two patches than with head, although only slightly better (16%) * This better compression for processed_b leads to slightly slower extraction (6-7%), and surprisingly slower extraction for length-and-offset than for all-lengths (about 2%). * in the patholgical case, length-and-offset was notably faster on Q1 than all-lengths (24%), and somewhat slower on Q2 (8%). I think this shows me that I don't understand what JSON keys are "at the end". * notably, length-and-offset when uncompressed (EXTERNAL) was faster on Q1 than head! This was surprising enough that I retested it. Overall, I'm satisfied with the performance of the length-and-offset patch. -- Josh Berkus PostgreSQL Experts Inc. http://pgexperts.com -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers