MDEV-7410 Temporary table name conflict between sessions

workaround for missing SP auto-reparse.
allow the user to disable stored_program_cache_size, if he wants

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

@@ -23,7 +23,7 @@ Warnings:
 Warning	1292	Truncated incorrect stored_program_cache value: '-1'
 SELECT @@global.stored_program_cache;
 @@global.stored_program_cache
-256
+0
 SET @@global.stored_program_cache =100000000000;
 Warnings:
 Warning	1292	Truncated incorrect stored_program_cache value: '100000000000'
@@ -31,11 +31,9 @@ SELECT @@global.stored_program_cache;
 @@global.stored_program_cache
 524288
 SET @@global.stored_program_cache = 0;
-Warnings:
-Warning	1292	Truncated incorrect stored_program_cache value: '0'
 SELECT @@global.stored_program_cache;
 @@global.stored_program_cache
-256
+0
 SET @@global.stored_program_cache = 10000.01;
 ERROR 42000: Incorrect argument type to variable 'stored_program_cache'
 SET @@global.stored_program_cache = ON;

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

+create procedure p1() select 1;
+flush status;
+show status like 'handler_read_key';
+Variable_name	Value
+Handler_read_key	0
+call p1;
+1
+1
+show status like 'handler_read_key';
+Variable_name	Value
+Handler_read_key	1
+call p1;
+1
+1
+show status like 'handler_read_key';
+Variable_name	Value
+Handler_read_key	1
+set global stored_program_cache=0;
+call p1;
+1
+1
+show status like 'handler_read_key';
+Variable_name	Value
+Handler_read_key	2
+call p1;
+1
+1
+show status like 'handler_read_key';
+Variable_name	Value
+Handler_read_key	3
+drop procedure p1;
+set global stored_program_cache=default;
+create procedure pr(i int) begin
+create table t1 (a int, b int);
+if (i = 1) then alter table t1 drop a;
+else alter table t1 drop b; 
+end if;
+select * from t1;
+drop table t1;
+end |
+call pr(1);
+b
+call pr(2);
+ERROR 42S22: Unknown column 'test.t1.b' in 'field list'
+drop table t1;
+set global stored_program_cache=0;
+call pr(1);
+b
+call pr(2);
+a
+drop procedure pr;
+set global stored_program_cache=default;

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

+create procedure p1() select 1;
+
+flush status;
+show status like 'handler_read_key';
+call p1;
+show status like 'handler_read_key';
+call p1;
+show status like 'handler_read_key';
+
+set global stored_program_cache=0;
+
+call p1;
+show status like 'handler_read_key';
+call p1;
+show status like 'handler_read_key';
+
+drop procedure p1;
+set global stored_program_cache=default;
+
+# Test for missing SP automatic reparsing.
+# when MDEV-5816 is implemented, it should be removed.
+
+--delimiter |
+create procedure pr(i int) begin
+  create table t1 (a int, b int);
+  if (i = 1) then alter table t1 drop a;
+  else alter table t1 drop b; 
+  end if;
+  select * from t1;
+  drop table t1;
+end |
+--delimiter ;
+call pr(1);
+--error ER_BAD_FIELD_ERROR
+call pr(2);
+drop table t1;
+
+set global stored_program_cache=0;
+call pr(1);
+call pr(2);
+drop procedure pr;
+set global stored_program_cache=default;
+

sql/sys_vars.cc

@@ -3679,7 +3679,7 @@ static Sys_var_ulong Sys_sp_cache_size(
        "The soft upper limit for number of cached stored routines for "
        "one connection.",
        GLOBAL_VAR(stored_program_cache_size), CMD_LINE(REQUIRED_ARG),
-       VALID_RANGE(256, 512 * 1024), DEFAULT(256), BLOCK_SIZE(1));
+       VALID_RANGE(0, 512 * 1024), DEFAULT(256), BLOCK_SIZE(1));
 
 export const char *plugin_maturity_names[]=
 { "unknown", "experimental", "alpha", "beta", "gamma", "stable", 0 };