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| author | Vicențiu Ciorbaru <vicentiu@mariadb.org> | 2021-03-28 21:09:51 +0300 |
|---|---|---|
| committer | Vicențiu Ciorbaru <vicentiu@mariadb.org> | 2021-04-21 14:08:58 +0300 |
| commit | 2d595319bf542dcdeeb058139efa2ef54f645c7b (patch) | |
| tree | 0b1386cd1340b2a2c175f45f12d64e35e945e1b9 /sql/sql_limit.h | |
| parent | 3fcc4f6fc24e8bde2f7d3a6aa162d69554bf8e6f (diff) | |
| download | mariadb-git-2d595319bf542dcdeeb058139efa2ef54f645c7b.tar.gz | |
cleanup: Select_limit_counters rename set_unlimited to clear
The function was originally introduced by eb0804ef5e7eeb059bb193c3c6787e8a4188d34d
MDEV-18553: MDEV-16327 pre-requisits part 1: isolation of LIMIT/OFFSET handling
set_unlimited had an overloaded notion of both clearing the offset value
and the limit value. The code is used for SQL_CALC_ROWS option to
disable the limit clause after the limit is reached, while at the same
time the calling code suppreses sending of rows.
Proposed solution:
Dedicated clear method for query initialization (to ensure no garbage
remains between executions).
Dedicated set_unlimited that only alters the limit value.
Diffstat (limited to 'sql/sql_limit.h')
| -rw-r--r-- | sql/sql_limit.h | 18 |
1 files changed, 16 insertions, 2 deletions
diff --git a/sql/sql_limit.h b/sql/sql_limit.h index 6f32e5d17e9..60034201a50 100644 --- a/sql/sql_limit.h +++ b/sql/sql_limit.h @@ -37,8 +37,13 @@ class Select_limit_counters { offset_limit_cnt= offset; select_limit_cnt= limit; - if (select_limit_cnt + offset_limit_cnt >= - select_limit_cnt) + /* + Guard against an overflow condition, where limit + offset exceede + ha_rows value range. This case covers unreasonably large parameter + values that do not have any practical use so assuming in this case + that the query does not have a limit is fine. + */ + if (select_limit_cnt + offset_limit_cnt >= select_limit_cnt) select_limit_cnt+= offset_limit_cnt; else select_limit_cnt= HA_POS_ERROR; @@ -52,7 +57,16 @@ class Select_limit_counters bool is_unlimited() const { return select_limit_cnt == HA_POS_ERROR; } + /* + Set the limit to allow returning an unlimited number of rows. Useful + for cases when we want to continue execution indefinitely after the limit + is reached (for example for SQL_CALC_ROWS extension). + */ void set_unlimited() + { select_limit_cnt= HA_POS_ERROR; } + + /* Reset the limit entirely. */ + void clear() { select_limit_cnt= HA_POS_ERROR; offset_limit_cnt= 0; } bool check_offset(ha_rows sent) const |