On Wed, Nov 13, 2019 at 9:48 AM Amit Kapila <amit.kapil...@gmail.com> wrote: > > Yeah, 0,2,3 and 4 sounds reasonable to me. Earlier, Dilip also got > confused with option 1. >
Let me try to summarize the discussion on this point and see if others have any opinion on this matter. We need a way to allow IndexAm to specify whether it can participate in a parallel vacuum. As we know there are two phases of index-vacuum, bulkdelete and vacuumcleanup and in many cases, the bulkdelete performs the main deletion work and then vacuumcleanup just returns index statistics. So, for such cases, we don't want the second phase to be performed by a parallel vacuum worker. Now, if the bulkdelete phase is not performed, then vacuumcleanup can process the entire index in which case it is better to do that phase via parallel worker. OTOH, in some cases vacuumcleanup takes another pass over-index to reclaim empty pages and update record the same in FSM even if bulkdelete is performed. This happens in gin and bloom indexes. Then, we have an index where we do all the work in cleanup phase like in the case of brin indexes. Now, for this category of indexes, we want vacuumcleanup phase to be also performed by a parallel worker. In short different indexes have different requirements for which phase of index vacuum can be performed in parallel. Just to be clear, we can't perform both the phases (bulkdelete and cleanup) in one-go as bulk-delete can happen multiple times on a large index whereas vacuumcleanup is done once at the end. Based on these needs, we came up with a way to allow users to specify this information for IndexAm's. Basically, Indexam will expose a variable amparallelvacuumoptions which can have below options VACUUM_OPTION_NO_PARALLEL 1 << 0 # vacuum (neither bulkdelete nor vacuumcleanup) can't be performed in parallel VACUUM_OPTION_PARALLEL_BULKDEL 1 << 1 # bulkdelete can be done in parallel (Indexes nbtree, hash, gin, gist, spgist, bloom will set this flag) VACUUM_OPTION_PARALLEL_COND_CLEANUP 1 << 2 # vacuumcleanup can be done in parallel if bulkdelete is not performed (Indexes nbtree, brin, gin, gist, spgist, bloom will set this flag) VACUUM_OPTION_PARALLEL_CLEANUP 1 << 3 # vacuumcleanup can be done in parallel even if bulkdelete is already performed (Indexes gin, brin, and bloom will set this flag) We have discussed to expose this information via two variables but the above seems like a better idea to all the people involved. Any suggestions? Anyone thinks this is not the right way to expose this information or there is no need to expose this information or they have a better idea for this? Sawada-San, Dilip, feel free to correct me. -- With Regards, Amit Kapila. EnterpriseDB: http://www.enterprisedb.com
