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Test for bug 578. And a comment in slave.cc.

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sql/slave.cc:
  Comment to remember that size of relay logs on disk is not the total size
  of the relay log.
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unknown
2003-06-05 17:02:00 +02:00
parent a3afb2bcbe
commit bd414c301c
4 changed files with 47 additions and 0 deletions
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20
sql/slave.cc
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@ -1186,6 +1186,26 @@ int init_relay_log_info(RELAY_LOG_INFO* rli, const char* info_fname)
strmov(strcend(tmp,'.'),"-relay-bin");
opt_relay_logname=my_strdup(tmp,MYF(MY_WME));
}
/*
The relay log will now be opened, as a SEQ_READ_APPEND IO_CACHE. It is
notable that the last kilobytes of it (8 kB for example) may live in memory,
not on disk (depending on what the thread using it does). While this is
efficient, it has a side-effect one must know:
the size of the relay log on disk (displayed by 'ls -l' on Unix) can be a
few kilobytes less than one would expect by doing SHOW SLAVE STATUS; this
happens when only the IO thread is started (not the SQL thread). The
"missing" kilobytes are in memory, are preserved during 'STOP SLAVE; START
SLAVE IO_THREAD', and are flushed to disk when the slave's mysqld stops. So
this does not cause any bug. Example of how disk size grows by leaps:
Read_Master_Log_Pos: 7811 -rw-rw---- 1 guilhem qq 4 Jun 5 16:19 gbichot2-relay-bin.002
...later...
Read_Master_Log_Pos: 9744 -rw-rw---- 1 guilhem qq 8192 Jun 5 16:27 gbichot2-relay-bin.002
See how 4 is less than 7811 and 8192 is less than 9744.
*/
if (open_log(&rli->relay_log, glob_hostname, opt_relay_logname,
"-relay-bin", opt_relaylog_index_name,
LOG_BIN, 1 /* read_append cache */,