From 4584b8d96e250d6e3cc854a279df80f654719d1f Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Thu, 2 Jul 2026 17:39:15 -0400 Subject: [PATCH v3 4/5] Remove useless check against lower bound in gbt_var_node_pf_match. Truncating an internal node's upper bound can cause it to compare less than some values that in fact are included in the represented leaf page. So we need a hack to make sure it looks large enough to include all values that could be on the page. But there's no equivalent issue for the lower bound. The fact that this code did a fuzzy comparison for the lower bound seems to be the result of fuzzy thinking. Or maybe there was a desire to not assume too much about what the datatype's comparison rule is; but we've already fully bought into the premise that internal keys compare like bytea. The comparable check in gbt_var_penalty() may also be useless, but I'm not quite sure. In any case that seems negligible from a performance standpoint, so I left it alone. Author: Tom Lane Discussion: https://postgr.es/m/AH*AvQCYKhQGVvPWi1GiU4oY.8.1781609375063.Hmail.3020001251@tju.edu.cn --- contrib/btree_gist/btree_utils_var.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) diff --git a/contrib/btree_gist/btree_utils_var.c b/contrib/btree_gist/btree_utils_var.c index 99919ca3974..f1b13741630 100644 --- a/contrib/btree_gist/btree_utils_var.c +++ b/contrib/btree_gist/btree_utils_var.c @@ -213,16 +213,14 @@ gbt_bytea_pf_match(const bytea *pf, const bytea *query, const gbtree_vinfo *tinf * If the data type is truncatable, then a shortened upper bound must be * considered to include all values that match it up to its own length, * even though longer values would normally be considered larger. - * - * XXX isn't the check against node->lower useless? - * A truncated lower bound would already be less than all included values. + * We don't need to check the lower bound though: shortening it just + * makes it even smaller. */ static bool gbt_var_node_pf_match(const GBT_VARKEY_R *node, const bytea *query, const gbtree_vinfo *tinfo) { return (tinfo->trnc && - (gbt_bytea_pf_match(node->lower, query, tinfo) || - gbt_bytea_pf_match(node->upper, query, tinfo))); + gbt_bytea_pf_match(node->upper, query, tinfo)); } -- 2.52.0