From 239abfff12a41a0611d24e2c7b67895a7359e6bf Mon Sep 17 00:00:00 2001 From: Andrew Gierth Date: Sat, 24 Nov 2018 09:59:49 +0000 Subject: [PATCH] Fix hstore hash function for empty hstores upgraded from 8.4. Hstore data generated on pg 8.4 and pg_upgraded to current versions remains in its original on-disk format unless modified. The same goes for values generated by the addon hstore-new module on pre-9.0 versions. (The hstoreUpgrade function converts old values on the fly when read in, but the on-disk value is not modified by this.) Since old-format empty hstores (and hstore-new hstores) have representations compatible with the new format, hstoreUpgrade thought it could get away without modifying such values; but this breaks hstore_hash (and the new hstore_hash_extended) which assumes bit-perfect matching between semantically identical hstore values. Only one bit actually differs (the "new version" flag in the count field) but that of course is enough to break the hash. Fix by making hstoreUpgrade unconditionally convert all old values to new format. Backpatch all the way, even though this changes a hash value in some cases, because in those cases the hash value is already failing - for example, a hash join between old- and new-format empty hstores will be failing to match, or a hash index on an hstore column containing an old-format empty value will be failing to find the value since it will be searching for a hash derived from a new-format datum. (There are no known field reports of this happening, probably because hashing of hstores has only been useful in limited circumstances and there probably isn't much upgraded data being used this way.) Per concerns arising from discussion of commit eb6f29141be. Original bug is my fault. Discussion: https://postgr.es/m/60b1fd3b-7332-40f0-7e7f-f2f04f777747%402ndquadrant.com --- contrib/hstore/hstore_compat.c | 47 ++++++++++++++-------------------- 1 file changed, 19 insertions(+), 28 deletions(-) diff --git a/contrib/hstore/hstore_compat.c b/contrib/hstore/hstore_compat.c index b95ce9b4aa..1d4e7484e4 100644 --- a/contrib/hstore/hstore_compat.c +++ b/contrib/hstore/hstore_compat.c @@ -238,34 +238,35 @@ hstoreUpgrade(Datum orig) HStore *hs = (HStore *) PG_DETOAST_DATUM(orig); int valid_new; int valid_old; - bool writable; /* Return immediately if no conversion needed */ - if ((hs->size_ & HS_FLAG_NEWVERSION) || - hs->size_ == 0 || + if (hs->size_ & HS_FLAG_NEWVERSION) + return hs; + + /* Do we have a writable copy? If not, make one. */ + if ((void *) hs == (void *) DatumGetPointer(orig)) + hs = (HStore *) PG_DETOAST_DATUM_COPY(orig); + + if (hs->size_ == 0 || (VARSIZE(hs) < 32768 && HSE_ISFIRST((ARRPTR(hs)[0])))) + { + HS_SETCOUNT(hs, HS_COUNT(hs)); + HS_FIXSIZE(hs, HS_COUNT(hs)); return hs; + } valid_new = hstoreValidNewFormat(hs); valid_old = hstoreValidOldFormat(hs); - /* Do we have a writable copy? */ - writable = ((void *) hs != (void *) DatumGetPointer(orig)); if (!valid_old || hs->size_ == 0) { if (valid_new) { /* - * force the "new version" flag and the correct varlena length, - * but only if we have a writable copy already (which we almost - * always will, since short new-format values won't come through - * here) + * force the "new version" flag and the correct varlena length. */ - if (writable) - { - HS_SETCOUNT(hs, HS_COUNT(hs)); - HS_FIXSIZE(hs, HS_COUNT(hs)); - } + HS_SETCOUNT(hs, HS_COUNT(hs)); + HS_FIXSIZE(hs, HS_COUNT(hs)); return hs; } else @@ -302,15 +303,10 @@ hstoreUpgrade(Datum orig) elog(WARNING, "ambiguous hstore value resolved as hstore-new"); /* - * force the "new version" flag and the correct varlena length, but - * only if we have a writable copy already (which we almost always - * will, since short new-format values won't come through here) + * force the "new version" flag and the correct varlena length. */ - if (writable) - { - HS_SETCOUNT(hs, HS_COUNT(hs)); - HS_FIXSIZE(hs, HS_COUNT(hs)); - } + HS_SETCOUNT(hs, HS_COUNT(hs)); + HS_FIXSIZE(hs, HS_COUNT(hs)); return hs; #else elog(WARNING, "ambiguous hstore value resolved as hstore-old"); @@ -318,13 +314,8 @@ hstoreUpgrade(Datum orig) } /* - * must have an old-style value. Overwrite it in place as a new-style one, - * making sure we have a writable copy first. + * must have an old-style value. Overwrite it in place as a new-style one. */ - - if (!writable) - hs = (HStore *) PG_DETOAST_DATUM_COPY(orig); - { int count = hs->size_; HEntry *new_entries = ARRPTR(hs); -- 2.40.0