Changed the default value for the system variable @@in_subquery_conversion_threshold.

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

@@ -1425,10 +1425,10 @@ ENUM_VALUE_LIST	NULL
 READ_ONLY	NO
 COMMAND_LINE_ARGUMENT	REQUIRED
 VARIABLE_NAME	IN_SUBQUERY_CONVERSION_THRESHOLD
-SESSION_VALUE	10000
-GLOBAL_VALUE	10000
+SESSION_VALUE	1000
+GLOBAL_VALUE	1000
 GLOBAL_VALUE_ORIGIN	COMPILE-TIME
-DEFAULT_VALUE	10000
+DEFAULT_VALUE	1000
 VARIABLE_SCOPE	SESSION
 VARIABLE_TYPE	BIGINT UNSIGNED
 VARIABLE_COMMENT	The minimum number of scalar elements in the value list of IN predicate that triggers its conversion to IN subquery

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

@@ -1551,10 +1551,10 @@ ENUM_VALUE_LIST	NULL
 READ_ONLY	NO
 COMMAND_LINE_ARGUMENT	REQUIRED
 VARIABLE_NAME	IN_SUBQUERY_CONVERSION_THRESHOLD
-SESSION_VALUE	10000
-GLOBAL_VALUE	10000
+SESSION_VALUE	1000
+GLOBAL_VALUE	1000
 GLOBAL_VALUE_ORIGIN	COMPILE-TIME
-DEFAULT_VALUE	10000
+DEFAULT_VALUE	1000
 VARIABLE_SCOPE	SESSION
 VARIABLE_TYPE	BIGINT UNSIGNED
 VARIABLE_COMMENT	The minimum number of scalar elements in the value list of IN predicate that triggers its conversion to IN subquery

sql/sys_vars.cc

@@ -5797,5 +5797,5 @@ static Sys_var_ulong Sys_in_subquery_conversion_threshold(
        "The minimum number of scalar elements in the value list of "
        "IN predicate that triggers its conversion to IN subquery",
        SESSION_VAR(in_subquery_conversion_threshold), CMD_LINE(OPT_ARG),
-       VALID_RANGE(0, ULONG_MAX), DEFAULT(10000), BLOCK_SIZE(1));
+       VALID_RANGE(0, ULONG_MAX), DEFAULT(1000), BLOCK_SIZE(1));