Lift restriction on setting read_only_error_msg_extra

Summary:
Per request, we allow setting read_only_error_msg_extra without being in
read_only state. The custom message can be set/reset at any time.

Squash with https://reviews.facebook.net/D61713
Squash with https://reviews.facebook.net/D61677 (for main.range* test results)

Test Plan: mtr

Reviewers: santoshb

Reviewed By: santoshb

Subscribers: webscalesql-eng

Differential Revision: https://reviews.facebook.net/D64125

Author: tianx

mysql-test/r/range_all.result

@@ -862,7 +862,7 @@ and c10 in ("abcdefgh", "123456789", "qwertyuio", "asddfgh",
 "abcdefgC", "12345678C", "qwertyuiC", "asddfgC");
 c1	c2	c3	c4	c5	c6	c7	c8	c9	c10	c11	c12	c13	c14	c15	c16
 Warnings:
-Warning	1927	Memory capacity of 1536000 bytes for 'range_optimizer_max_mem_size' exceeded. Range optimization was not done for this query.
+Warning	1926	Memory capacity of 1536000 bytes for 'range_optimizer_max_mem_size' exceeded. Range optimization was not done for this query.
 drop table t1;
 End of 4.1 tests
 CREATE TABLE t1 (

mysql-test/r/range_icp.result

@@ -862,7 +862,7 @@ and c10 in ("abcdefgh", "123456789", "qwertyuio", "asddfgh",
 "abcdefgC", "12345678C", "qwertyuiC", "asddfgC");
 c1	c2	c3	c4	c5	c6	c7	c8	c9	c10	c11	c12	c13	c14	c15	c16
 Warnings:
-Warning	1927	Memory capacity of 1536000 bytes for 'range_optimizer_max_mem_size' exceeded. Range optimization was not done for this query.
+Warning	1926	Memory capacity of 1536000 bytes for 'range_optimizer_max_mem_size' exceeded. Range optimization was not done for this query.
 drop table t1;
 End of 4.1 tests
 CREATE TABLE t1 (

mysql-test/r/range_icp_mrr.result

@@ -862,7 +862,7 @@ and c10 in ("abcdefgh", "123456789", "qwertyuio", "asddfgh",
 "abcdefgC", "12345678C", "qwertyuiC", "asddfgC");
 c1	c2	c3	c4	c5	c6	c7	c8	c9	c10	c11	c12	c13	c14	c15	c16
 Warnings:
-Warning	1927	Memory capacity of 1536000 bytes for 'range_optimizer_max_mem_size' exceeded. Range optimization was not done for this query.
+Warning	1926	Memory capacity of 1536000 bytes for 'range_optimizer_max_mem_size' exceeded. Range optimization was not done for this query.
 drop table t1;
 End of 4.1 tests
 CREATE TABLE t1 (

mysql-test/r/range_mrr.result

@@ -862,7 +862,7 @@ and c10 in ("abcdefgh", "123456789", "qwertyuio", "asddfgh",
 "abcdefgC", "12345678C", "qwertyuiC", "asddfgC");
 c1	c2	c3	c4	c5	c6	c7	c8	c9	c10	c11	c12	c13	c14	c15	c16
 Warnings:
-Warning	1927	Memory capacity of 1536000 bytes for 'range_optimizer_max_mem_size' exceeded. Range optimization was not done for this query.
+Warning	1926	Memory capacity of 1536000 bytes for 'range_optimizer_max_mem_size' exceeded. Range optimization was not done for this query.
 drop table t1;
 End of 4.1 tests
 CREATE TABLE t1 (

mysql-test/r/range_mrr_cost.result

@@ -862,7 +862,7 @@ and c10 in ("abcdefgh", "123456789", "qwertyuio", "asddfgh",
 "abcdefgC", "12345678C", "qwertyuiC", "asddfgC");
 c1	c2	c3	c4	c5	c6	c7	c8	c9	c10	c11	c12	c13	c14	c15	c16
 Warnings:
-Warning	1927	Memory capacity of 1536000 bytes for 'range_optimizer_max_mem_size' exceeded. Range optimization was not done for this query.
+Warning	1926	Memory capacity of 1536000 bytes for 'range_optimizer_max_mem_size' exceeded. Range optimization was not done for this query.
 drop table t1;
 End of 4.1 tests
 CREATE TABLE t1 (

mysql-test/r/range_none.result

@@ -861,7 +861,7 @@ and c10 in ("abcdefgh", "123456789", "qwertyuio", "asddfgh",
 "abcdefgC", "12345678C", "qwertyuiC", "asddfgC");
 c1	c2	c3	c4	c5	c6	c7	c8	c9	c10	c11	c12	c13	c14	c15	c16
 Warnings:
-Warning	1927	Memory capacity of 1536000 bytes for 'range_optimizer_max_mem_size' exceeded. Range optimization was not done for this query.
+Warning	1926	Memory capacity of 1536000 bytes for 'range_optimizer_max_mem_size' exceeded. Range optimization was not done for this query.
 drop table t1;
 End of 4.1 tests
 CREATE TABLE t1 (

mysql-test/r/range_with_memory_limit.result

@@ -1,5 +1,7 @@
-set @@global.read_only_error_msg_extra='Not in read_only';
-ERROR HY000: The system variable read_only_error_msg_extra can only be set in read-only (super) status.
+set @@global.read_only_error_msg_extra='Custom message before read_only';
+select @@global.read_only_error_msg_extra;
+@@global.read_only_error_msg_extra
+Custom message before read_only
 set global read_only = true;
 set @@global.read_only_error_msg_extra = default;
 select @@global.read_only_error_msg_extra;

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

@@ -1,8 +1,7 @@
 --source include/not_embedded.inc
 
-# Cannot set the value if server is not in read_only
---error ER_VARIABLE_NOT_SETTABLE_WITHOUT_READ_ONLY
-set @@global.read_only_error_msg_extra='Not in read_only';
+set @@global.read_only_error_msg_extra='Custom message before read_only';
+select @@global.read_only_error_msg_extra;
 
 set global read_only = true;
 set @@global.read_only_error_msg_extra = default;

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

@@ -7230,9 +7230,6 @@ ER_CONNECTION_TIMEOUT
 ER_OPTION_PREVENTS_STATEMENT_EXTRA_INFO
   eng "The MySQL server is running with the %s option so it cannot execute this statement. %s"
 
-ER_VARIABLE_NOT_SETTABLE_WITHOUT_READ_ONLY
-  eng "The system variable %.200s can only be set in read-only (super) status."
-
 ER_CAPACITY_EXCEEDED
   eng "Memory capacity of %llu bytes for '%s' exceeded. %s"
 

sql/share/errmsg-utf8.txt

@@ -5543,22 +5543,9 @@ static Sys_var_uint Sys_select_into_file_fsync_timeout(
        SESSION_VAR(select_into_file_fsync_timeout), CMD_LINE(OPT_ARG),
        VALID_RANGE(0, UINT_MAX), DEFAULT(0), BLOCK_SIZE(1));
 
-static bool check_read_only_error_msg_extra(
-    sys_var *self, THD *thd, set_var *var)
-{
-  if (!opt_readonly && !opt_super_readonly)
-  {
-    my_error(ER_VARIABLE_NOT_SETTABLE_WITHOUT_READ_ONLY,
-             MYF(0),
-             var->var->name.str);
-    return true;
-  }
-  return false;
-}
 static Sys_var_charptr Sys_read_only_error_msg_extra(
        "read_only_error_msg_extra",
        "Set this variable to print out extra error information, "
        "which will be appended to read_only error messages.",
        GLOBAL_VAR(opt_read_only_error_msg_extra), CMD_LINE(OPT_ARG),
-       IN_SYSTEM_CHARSET, DEFAULT(""), NO_MUTEX_GUARD, NOT_IN_BINLOG,
-       ON_CHECK(check_read_only_error_msg_extra));
+       IN_SYSTEM_CHARSET, DEFAULT(""), NO_MUTEX_GUARD, NOT_IN_BINLOG);