I brought this up in [1] but wanted to start a dedicated thread. Since 16fa9b2b30a357 GiST indexes are not built in shared buffers. However, smgrimmedsync() is not done anywhere and skipFsync=true is always passed to smgrwrite() and smgrextend(). So, if a checkpoint starts and finishes after WAL-logging some of the index build pages and there is a crash sometime before the dirty pages make it to permanent storage, won't that data be lost?
(Also, as Heikki has pointed out before, passing skipFsync=false isn't sufficient either if checkpoint finishes before register_dirty_segment(), so seems like smgrimmesync() is needed.) Seems like the following would address this: diff --git a/src/backend/access/gist/gistbuild.c b/src/backend/access/gist/gistbuild.c index 9854116fca..364a7455ea 100644 --- a/src/backend/access/gist/gistbuild.c +++ b/src/backend/access/gist/gistbuild.c @@ -454,9 +454,11 @@ gist_indexsortbuild(GISTBuildState *state) smgrwrite(RelationGetSmgr(state->indexrel), MAIN_FORKNUM, GIST_ROOT_BLKNO, pagestate->page, true); if (RelationNeedsWAL(state->indexrel)) + { log_newpage(&state->indexrel->rd_node, MAIN_FORKNUM, GIST_ROOT_BLKNO, pagestate->page, true); - + smgrimmedsync(RelationGetSmgr(state->indexrel), MAIN_FORKNUM); + } pfree(pagestate->page); pfree(pagestate); } - Melanie [1] https://www.postgresql.org/message-id/CAAKRu_ZmkCNz-%3D5U5wZyyi3%3DUsfs1btsTKc_L9r1ceFvbxE3kg%40mail.gmail.com