backport of guilhem@mysql.com-20100628140739-i9vy8ugxp1v5aspb

from next-mr-bugfixing:
BUG#54682 "set sql_select_limit=0 does not work"; let SQL_SELECT_LIMIT=0
work like it does in 5.1.


mysql-test/suite/sys_vars/r/sql_select_limit_func.result:
  before the fix, the SET would emit a warning (0 being rounded up to 1)
  and SELECTs would return one row.
sql/sys_vars.cc:
  0 is allowed, it means an implicit LIMIT 0 (i.e. no rows returned)

mysql-test/suite/sys_vars/r/sql_select_limit_func.result

@@ -62,6 +62,16 @@ a	b	a	b
 6	val6	6	val6
 affected rows: 2
 Expecting affected rows: 2
+SET SESSION sql_select_limit = 0;
+affected rows: 0
+SELECT * FROM t1;
+a	b
+affected rows: 0
+Expecting affected rows: 0
+SELECT * FROM t1 INNER JOIN t2 ON t1.a = t2.a;
+a	b	a	b
+affected rows: 0
+Expecting affected rows: 0
 '#-----------------------------FN_DYNVARS_165_03---------------#'
 SET SESSION sql_select_limit = 2;
 affected rows: 0

mysql-test/suite/sys_vars/t/sql_select_limit_func.test

@@ -86,6 +86,14 @@ SELECT * FROM t1;
 SELECT * FROM t1 INNER JOIN t2 ON t1.a = t2.a;
 --echo Expecting affected rows: 2
 
+SET SESSION sql_select_limit = 0;
+
+SELECT * FROM t1;
+--echo Expecting affected rows: 0
+
+SELECT * FROM t1 INNER JOIN t2 ON t1.a = t2.a;
+--echo Expecting affected rows: 0
+
 --echo '#-----------------------------FN_DYNVARS_165_03---------------#'
 #
 # Small value with LIMIT Clause

sql/sys_vars.cc

@@ -2379,7 +2379,7 @@ static Sys_var_harows Sys_select_limit(
        "sql_select_limit",
        "The maximum number of rows to return from SELECT statements",
        SESSION_VAR(select_limit), NO_CMD_LINE,
-       VALID_RANGE(1, HA_POS_ERROR), DEFAULT(HA_POS_ERROR), BLOCK_SIZE(1));
+       VALID_RANGE(0, HA_POS_ERROR), DEFAULT(HA_POS_ERROR), BLOCK_SIZE(1));
 
 static bool update_timestamp(THD *thd, set_var *var)
 {