From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Tue, 15 May 2018 22:05:12 +0300 From: Konstantin Osipov Subject: Re: [PATCH 1/4] vinyl: fix EQ check in run iterator Message-ID: <20180515190512.GA24119@atlas> References: <6028746ee469d1ba463c1e9740e27a3516ffc7f7.1526392563.git.vdavydov.dev@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6028746ee469d1ba463c1e9740e27a3516ffc7f7.1526392563.git.vdavydov.dev@gmail.com> To: Vladimir Davydov Cc: tarantool-patches@freelists.org List-ID: * Vladimir Davydov [18/05/15 17:10]: I am pushing this as is now, please a couple of comments below. > vy_run_iterator_seek() is supposed to check that the resulting statement > matches the search key in case of ITER_EQ, but if the search key lies at > the beginning of the slice, it doesn't. As a result, vy_point_lookup() > may fail to find an existing tuple as demonstrated below. > > Suppose we are looking for key {10} in the primary index which consists > of an empty mem and two runs: > > run 1: DELETE{15} > run 2: INSERT{10} > > vy_run_iterator_next() returns DELETE{15} for run 1 because of the > missing EQ check and vy_point_lookup() stops at run 1 (since the > terminal statement is found) and mistakenly returns NULL. > > The issue manifests itself as crash in vinyl_iterator_secondary_next(), > when we fail to find the tuple in the primary index corresponding to a > statement found in a secondary index. I believe this explanation belongs to the code, not only to the changeset comment. Ideally, this special case should be covered in a unit test, not just in the code or in CS comment. > Part of #3393 > --- > src/box/vy_run.c | 13 ++++++++++++- > 1 file changed, 12 insertions(+), 1 deletion(-) > > diff --git a/src/box/vy_run.c b/src/box/vy_run.c > index 587cb002..8c922895 100644 > --- a/src/box/vy_run.c > +++ b/src/box/vy_run.c > @@ -1316,6 +1316,7 @@ vy_run_iterator_seek(struct vy_run_iterator *itr, > { > const struct key_def *cmp_def = itr->cmp_def; > struct vy_slice *slice = itr->slice; > + const struct tuple *check_eq_key = NULL; > int cmp; > > if (slice->begin != NULL && > @@ -1340,6 +1341,8 @@ vy_run_iterator_seek(struct vy_run_iterator *itr, > return 0; > } > if (cmp < 0 || (cmp == 0 && iterator_type != ITER_GT)) { > + if (iterator_type == ITER_EQ) > + check_eq_key = key; > iterator_type = ITER_GE; > key = slice->begin; > } > @@ -1365,7 +1368,15 @@ vy_run_iterator_seek(struct vy_run_iterator *itr, > } > } > > - return vy_run_iterator_do_seek(itr, iterator_type, key, ret); > + if (vy_run_iterator_do_seek(itr, iterator_type, key, ret) != 0) > + return -1; > + > + if (check_eq_key != NULL && *ret != NULL && > + vy_stmt_compare(check_eq_key, *ret, cmp_def) != 0) { > + vy_run_iterator_stop(itr); > + *ret = NULL; > + } As far as I understand the code flow, this adds an extra check for cases when key != slice->begin. This is 99.9% of cases. Can we avoid an extra check if it is not needed? > + return 0; > } -- Konstantin Osipov, Moscow, Russia, +7 903 626 22 32 http://tarantool.io - www.twitter.com/kostja_osipov