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pgsql: Document nbtree row comparison design. 2+ messages / 1 participants [nested] [flat]
* pgsql: Document nbtree row comparison design. @ 2025-11-02 20:28 Peter Geoghegan <pg@bowt.ie> 0 siblings, 0 replies; 2+ messages in thread From: Peter Geoghegan @ 2025-11-02 20:28 UTC (permalink / raw) To: pgsql-committers@lists.postgresql.org Document nbtree row comparison design. Add comments explaining when and where it is safe for nbtree to treat row compare keys as if they were simple scalar inequality keys on the row's most significant column. This is particularly important within _bt_advance_array_keys, which deals with required inequality keys in a general and uniform way, without any special handling for row compares. Also spell out the implications of _bt_check_rowcompare's approach of _conditionally_ evaluating lower-order row compare subkeys, particularly when one of its lower-order subkeys might see NULL index tuple values (these may or may not affect whether the qual as a whole is satisfied). The behavior in this area isn't particularly intuitive, so these issues seem worth going into. In passing, add a few more defensive/documenting row comparison related assertions to _bt_first and _bt_check_rowcompare. Follow-up to commits bd3f59fd and ec986020. Author: Peter Geoghegan <pg@bowt.ie> Reviewed-By: Victor Yegorov <vyegorov@gmail.com> Reviewed-By: Chao Li <li.evan.chao@gmail.com> Discussion: https://postgr.es/m/CAH2-Wznwkak_K7pcAdv9uH8ZfNo8QO7+tHXOaCUddMeTfaCCFw@mail.gmail.com Backpatch-through: 18 Branch ------ master Details ------- https://git.postgresql.org/pg/commitdiff/b8f1c62807a58dc97e9262a17e7d0cadb305322b Modified Files -------------- src/backend/access/nbtree/nbtsearch.c | 8 +++-- src/backend/access/nbtree/nbtutils.c | 63 ++++++++++++++++++++++++++++++----- 2 files changed, 60 insertions(+), 11 deletions(-) ^ permalink raw reply [nested|flat] 2+ messages in thread
* pgsql: Document nbtree row comparison design. @ 2025-11-02 20:28 Peter Geoghegan <pg@bowt.ie> 0 siblings, 0 replies; 2+ messages in thread From: Peter Geoghegan @ 2025-11-02 20:28 UTC (permalink / raw) To: pgsql-committers@lists.postgresql.org Document nbtree row comparison design. Add comments explaining when and where it is safe for nbtree to treat row compare keys as if they were simple scalar inequality keys on the row's most significant column. This is particularly important within _bt_advance_array_keys, which deals with required inequality keys in a general and uniform way, without any special handling for row compares. Also spell out the implications of _bt_check_rowcompare's approach of _conditionally_ evaluating lower-order row compare subkeys, particularly when one of its lower-order subkeys might see NULL index tuple values (these may or may not affect whether the qual as a whole is satisfied). The behavior in this area isn't particularly intuitive, so these issues seem worth going into. In passing, add a few more defensive/documenting row comparison related assertions to _bt_first and _bt_check_rowcompare. Follow-up to commits bd3f59fd and ec986020. Author: Peter Geoghegan <pg@bowt.ie> Reviewed-By: Victor Yegorov <vyegorov@gmail.com> Reviewed-By: Chao Li <li.evan.chao@gmail.com> Discussion: https://postgr.es/m/CAH2-Wznwkak_K7pcAdv9uH8ZfNo8QO7+tHXOaCUddMeTfaCCFw@mail.gmail.com Backpatch-through: 18 Branch ------ REL_18_STABLE Details ------- https://git.postgresql.org/pg/commitdiff/6c3b1df878a65bb76e21ed640add30391db8f1d7 Modified Files -------------- src/backend/access/nbtree/nbtsearch.c | 8 +++-- src/backend/access/nbtree/nbtutils.c | 61 ++++++++++++++++++++++++++++++----- 2 files changed, 58 insertions(+), 11 deletions(-) ^ permalink raw reply [nested|flat] 2+ messages in thread
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