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https://issues.apache.org/jira/browse/COUCHDB-2804?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14737180#comment-14737180
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Mike Wallace commented on COUCHDB-2804:
---------------------------------------
In case anyone is interested, I did some (very handwavy) testing against the
admin port to see how much of a speedup the fast_view optimisation gives us - I
was typically getting results along these lines:
{code}
Raw changes: 1.702s
Filtered changes: 53.113s
Filtered-by-view changes: 57.041s
Fast-view changes: 9.500s
{code}
So it's certainly a valuable speed up.
(usual disclaimers apply - these figures were *not* obtained using science)
> The fast_view optimisation for view-filtered changes feeds is not
> cluster-aware
> -------------------------------------------------------------------------------
>
> Key: COUCHDB-2804
> URL: https://issues.apache.org/jira/browse/COUCHDB-2804
> Project: CouchDB
> Issue Type: Bug
> Security Level: public(Regular issues)
> Components: Database Core
> Affects Versions: 2.0.0
> Reporter: Mike Wallace
>
> The view changes functionality (the most up-to-date documentation I am aware
> of being here: https://github.com/rcouch/rcouch/wiki/View-Changes) needs some
> work to make the fast_view optimisation work via the clustered interface.
> This has been tested using the following script:
> https://gist.github.com/mikewallace1979/1f53f186e48bb888c256#file-test_fast_view-sh
> Running it against the admin port on 15986 produces a successful response [1]
> although people with an eye for detail will notice a secondary bug where the
> first change isn't included.
> Running it against the clustered port on 15984 produces a stack trace [2]:
> {code}
> {"error":"error","reason":"{function_clause,nil,\n
> [{couch_changes,filter,\n
> [{db,<26600.3277.0>,nil,<<\"1441816974537529\">>,<26600.3259.0>,\n
> #Ref<26600.0.0.19015>,\n {db_header,6,1,0,\n
> {4310,{1,0,{size_info,68,105}},96},\n {4406,1,93},\n
> {21426,[],1273},\n
> 0,nil,nil,1000,<<\"585e0d4edddc04b8423fee965a730e4c\">>,\n
> [{'[email protected]',0}],\n 0},\n 1,\n
> {btree,<26600.3259.0>,\n
> {4310,{1,0,{size_info,68,105}},96},\n
> #Fun<couch_db_updater.btree_by_id_split.1>,\n
> #Fun<couch_db_updater.btree_by_id_join.2>,undefined,\n
> #Fun<couch_db_updater.btree_by_id_reduce.2>,snappy},\n
> {btree,<26600.3259.0>,\n {4406,1,93},\n
> #Fun<couch_db_updater.btree_by_seq_split.1>,\n
> #Fun<couch_db_updater.btree_by_seq_join.2>,undefined,\n
> #Fun<couch_db_updater.btree_by_seq_reduce.2>,snappy},\n
> {btree,<26600.3259.0>,\n {21426,[],1273},\n
> undefined,undefined,undefined,nil,snappy},\n
> 1,<<\"shards/c0000000-dfffffff/test_db.1441816974\">>,\n
> \"/Users/mikewallace/src/asf/couchdb/dev/lib/node2/data/shards/c0000000-dfffffff/test_db.1441816974.couch\",\n
> undefined,[],nil,\n
> {user_ctx,null,[],undefined},\n nil,1000,\n
> [before_header,after_header,on_file_open],\n [create],\n
> snappy,nil,nil},\n {doc_info,<<\"doge\">>,1,\n
> [{rev_info,\n {1,\n
> <<174,50,232,100,203,90,27,198,130,81,79,221,160,216,74,\n
> 128>>},\n 1,false,4242}]},\n
> {fast_view,main_only,\n {doc,<<\"_design/fastview\">>,\n
> {1,\n
> [<<8,240,229,73,29,55,237,140,209,212,55,78,252,52,73,20>>]},\n
> {[{<<\"views\">>,\n {[{<<\"doge\">>,\n
> {[{<<\"map\">>,\n <<\"function(doc) { if
> (true) { emit(doc.id, 1); }};\">>}]}}]}},\n
> {<<\"options\">>,{[{<<\"seq_indexed\">>,true}]}}]},\n
> [],false,[]},\n <<\"doge\">>}],\n
> [{file,\"src/couch_changes.erl\"},{line,243}]},\n
> {fabric_rpc,changes_enumerator,2,\n
> [{file,\"src/fabric_rpc.erl\"},{line,328}]},\n
> {couch_btree,stream_kv_node2,8,[{file,\"src/couch_btree.erl\"},{line,783}]},\n
> {couch_btree,fold,4,[{file,\"src/couch_btree.erl\"},{line,220}]},\n
> {couch_db,changes_since,5,[{file,\"src/couch_db.erl\"},{line,1225}]},\n
> {fabric_rpc,changes,4,[{file,\"src/fabric_rpc.erl\"},{line,68}]},\n
> {rexi_server,init_p,3,[{file,\"src/rexi_server.erl\"},{line,139}]}]}"}
> {code}
> So it looks like we need to do a bit of work in fabric to make it aware of
> the fast_view optimisation.
> [1]
> https://gist.github.com/mikewallace1979/1f53f186e48bb888c256#file-output_admin_port-md
> [2]
> https://gist.github.com/mikewallace1979/1f53f186e48bb888c256#file-output_cluster_port-md
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