From e35244d626a14d2574efbee5c5db0dfec27cb8aa Mon Sep 17 00:00:00 2001 From: unknown Date: Thu, 14 Apr 2005 17:47:48 -0700 Subject: [PATCH] Add a comment to update_ref_and_keys --- sql/sql_select.cc | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/sql/sql_select.cc b/sql/sql_select.cc index 8031a99f4d1..a54294f00c0 100644 --- a/sql/sql_select.cc +++ b/sql/sql_select.cc @@ -3161,10 +3161,14 @@ update_ref_and_keys(THD *thd, DYNAMIC_ARRAY *keyuse,JOIN_TAB *join_tab, } /* - Special treatment for ft-keys. - Remove the following things from KEYUSE: + Sort the array of possible keys and remove the following key parts: - ref if there is a keypart which is a ref and a const. - - keyparts without previous keyparts. + (e.g. if there is a key(a,b) and the clause is a=3 and b=7 and b=t2.d, + then we skip the key part corresponding to b=t2.d) + - keyparts without previous keyparts + (e.g. if there is a key(a,b,c) but only b < 5 (or a=2 and c < 3) is + used in the query, we drop the partial key parts from consideration). + Special treatment for ft-keys. */ if (keyuse->elements) {