Comments on: Does anybody really know what time it is?

By: haimin life trace » Blog Archive » mysql æ—¶é—´çŸ¥å¤šå°‘

haimin life trace » Blog Archive » mysql æ—¶é—´çŸ¥å¤šå°‘ — Tue, 21 Oct 2008 07:53:27 +0000

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By: lamarche

lamarche — Mon, 20 Oct 2008 20:38:13 +0000

Just to make sure that utc_timestamp() is replication safe, I did the following test:

### On master

mysql> create table test as select now(), sysdate(), utc_timestamp();
Query OK, 1 row affected (0.04 sec)
Records: 1 Duplicates: 0 Warnings: 0

### I then restarted the slave and saw that utc_timestamp is replication safe:

mysql> select * from test;
+———————+———————+———————+
| now() | sysdate() | utc_timestamp() |
+———————+———————+———————+
| 2008-10-20 16:12:28 | 2008-10-20 16:12:28 | 2008-10-20 20:12:28 |
+———————+———————+———————+
1 row in set (0.00 sec)

By: Mats Kindahl

Mats Kindahl — Thu, 09 Oct 2008 20:06:50 +0000

Note that it is also possible to write replication-safe code by assigning non-deterministic values to user-defined variables. In other words, the following code replication-safe:

SET @foo = SYSDATE();
INSERT INTO t1 VALUES (@foo);

By: Scott

Scott — Thu, 09 Oct 2008 19:45:06 +0000

I suppose you could exploit that fact to keep a record of how far your slaves tend to lag behind, if you were interested in such statistics.

By: Sheeri Cabral

Sheeri Cabral — Thu, 09 Oct 2008 19:01:16 +0000

whoops! Fixing the post now. Thanx!

By: Roland Bouman

Roland Bouman — Thu, 09 Oct 2008 18:23:33 +0000

Hi!

“…Note that replication does not work well with deterministic functions…”

slip of the keyboard…should be *non-deterministic* functions.

In MySQL 5.1, it should be ok for replication when using mixed or row-based binary logging. In this case, the resultant value of the non-deterministic function call is logged instead of the fact that the call was made. So, the slave does not get to execute the call but gets passed the value resulting from the master’s call.

regards,

Roland