SQL, Tests: temporal_current_timestamp for setting default AS OF timestamp [closes #117]

mysql-test/suite/versioning/r/variables.result

+create table t (a int) with system versioning;
+insert into t values (1);
+update t set a=2;
+select * from t;
+a
+2
+show variables where Variable_name like "temporal_current_timestamp%";
+Variable_name	Value
+temporal_current_timestamp	now
+set global temporal_current_timestamp = '2031-1-1 0:0:0';
+select * from t;
+a
+2
+set global temporal_current_timestamp = '2011-1-1 0:0:0';
+select * from t;
+a
+set global temporal_current_timestamp = 'all';
+select * from t;
+a
+2
+1
+show variables where Variable_name like "temporal_current_timestamp%";
+Variable_name	Value
+temporal_current_timestamp	all
+create view vt as select * from t;
+select * from t;
+a
+2
+1
+drop view vt;
+select * from (select * from t) as tt;
+a
+2
+1
+set session temporal_current_timestamp = 'now';
+ERROR HY000: Variable 'temporal_current_timestamp' is a GLOBAL variable and should be set with SET GLOBAL
+drop table t;
+set global temporal_current_timestamp = 'now';

mysql-test/suite/versioning/t/variables.test

+create table t (a int) with system versioning;
+insert into t values (1);
+update t set a=2;
+
+select * from t;
+show variables where Variable_name like "temporal_current_timestamp%";
+
+set global temporal_current_timestamp = '2031-1-1 0:0:0';
+select * from t;
+
+set global temporal_current_timestamp = '2011-1-1 0:0:0';
+select * from t;
+
+set global temporal_current_timestamp = 'all';
+select * from t;
+show variables where Variable_name like "temporal_current_timestamp%";
+
+create view vt as select * from t;
+select * from t;
+drop view vt;
+
+select * from (select * from t) as tt;
+
+--error ER_GLOBAL_VARIABLE
+set session temporal_current_timestamp = 'now';
+
+drop table t;
+set global temporal_current_timestamp = 'now';

sql/mysqld.cc

@@ -781,6 +781,9 @@ char *relay_log_info_file, *report_user, *report_password, *report_host;
 char *opt_relay_logname = 0, *opt_relaylog_index_name=0;
 char *opt_logname, *opt_slow_logname, *opt_bin_logname;
 
+/* System Versioning */
+char *temporal_current_timestamp;
+
 /* Static variables */
 
 static volatile sig_atomic_t kill_in_progress;

sql/mysqld.h

@@ -175,6 +175,7 @@ extern char *opt_backup_history_logname, *opt_backup_progress_logname,
             *opt_backup_settings_name;
 extern const char *log_output_str;
 extern const char *log_backup_output_str;
+extern char *temporal_current_timestamp;
 extern char *mysql_home_ptr, *pidfile_name_ptr;
 extern MYSQL_PLUGIN_IMPORT char glob_hostname[FN_REFLEN];
 extern char mysql_home[FN_REFLEN];

sql/sql_select.cc

@@ -62,6 +62,7 @@
 #include <my_bit.h>
 #include <hash.h>
 #include <ft_global.h>
+#include "sys_vars_shared.h"
 
 /*
   A key part number that means we're using a fulltext scan.
@@ -775,6 +776,28 @@ int vers_setup_select(THD *thd, TABLE_LIST *tables, COND **where_expr,
         DBUG_RETURN(-1);
       }
 
+      if (vers_conditions.type == FOR_SYSTEM_TIME_UNSPECIFIED)
+      {
+        const char var[]= "temporal_current_timestamp";
+        sys_var *sv= intern_find_sys_var(var, sizeof(var) - 1);
+        DBUG_ASSERT(sv);
+        const char *data= *(char **)sv->option.value;
+        DBUG_ASSERT(data);
+        if (0 == strcmp(data, "all"))
+        {
+          vers_conditions.init(FOR_SYSTEM_TIME_ALL, UNIT_TIMESTAMP);
+        }
+        else if (0 != strcmp(data, "now"))
+        {
+          Item *ts= create_temporal_literal(thd, data, strlen(data),
+                                            system_charset_info,
+                                            MYSQL_TYPE_DATETIME, true);
+          if (!ts)
+            DBUG_RETURN(-1);
+          vers_conditions.init(FOR_SYSTEM_TIME_AS_OF, UNIT_TIMESTAMP, ts);
+        }
+      }
+
       if (vers_conditions.type != FOR_SYSTEM_TIME_UNSPECIFIED)
       {
         switch (slex->lock_type)

sql/sys_vars.cc

@@ -382,6 +382,11 @@ static Sys_var_charptr Sys_basedir(
        READ_ONLY GLOBAL_VAR(mysql_home_ptr), CMD_LINE(REQUIRED_ARG, 'b'),
        IN_FS_CHARSET, DEFAULT(0));
 
+static Sys_var_charptr sys_temporal_current_timestamp(
+       "temporal_current_timestamp", "Default AS OF value for versioned tables",
+       GLOBAL_VAR(temporal_current_timestamp), CMD_LINE(REQUIRED_ARG, 'b'),
+       IN_FS_CHARSET, DEFAULT("now"));
+
 static Sys_var_ulonglong Sys_binlog_cache_size(
        "binlog_cache_size", "The size of the transactional cache for "
        "updates to transactional engines for the binary log. "