On Fri, Mar 12, 2021 at 3:13 AM Andres Freund <and...@anarazel.de> wrote: > > Hi, > > On 2021-03-11 17:44:37 +0900, Masahiko Sawada wrote: > > The execution time of REFRESH MATERIALIZED VIEW are: > > > > w/ HEAP_INSERT_FROZEN flag : 42 sec > > w/o HEAP_INSERT_FROZEN flag : 33 sec > > > > After investigation, I found that such performance degradation happens > > on only HEAD code. It seems to me that commit 39b66a91b (and > > 7db0cd2145) is relevant that has heap_insert() set VM bits and > > PD_ALL_VISIBLE if HEAP_INSERT_FROZEN is specified (so CCing Tomas > > Vondra and authors). Since heap_insert() sets PD_ALL_VISIBLE to the > > page when inserting a tuple for the first time on the page (around > > L2133 in heapam.c), every subsequent heap_insert() on the page reads > > and pins a VM buffer (see RelationGetBufferForTuple()). Reading and > > pinning a VM buffer for every insertion is a very high cost. This > > doesn't happen in heap_multi_insert() since it sets VM buffer after > > filling the heap page with tuples. Therefore, there is no such > > performance degradation between COPY and COPY FREEZE if they use > > heap_multi_insert() (i.g., CIM_MULTI). Paul also reported it in that > > thread. > > Probably worth adding as an open item for 14.
I've added it to PostgreSQL 14 Open Items. Regards, -- Masahiko Sawada EDB: https://www.enterprisedb.com/
