Dear List,
it's time to ask my next long question regarding the myi-structure. From
the interals documentation I learned that the status information
consists (beside others) of the parts that I try to interpret in the
following. Please let me know, wether my interpretion is correct or
correct it.
Thanx a lot, Hagen
Name Size Dump
---- ---- ----
---------------------------------------------------------------------
state->open_count 2 00 01
*** I assume, that this value shows how often the MYI-File is opened by paralle processes.
***
---------------------------------------------------------------------
state->changed 1 39
*** I assume that this is only a flag but do not understand why it is 39 here.
Furthermore, If I reboot my machine, the value stays 39 but the description says that it
should be reseted. So I'am a little bit confused ;-) ***
---------------------------------------------------------------------
state->sortkey 1 FF
*** Is this a relict ??? It is not used but available. ***
---------------------------------------------------------------------
state->state.records 8 00 00 00 00 00 00 00 02
*** Thats easy to understand, but does this mean, that MyISAM allows "only"
18446744073709551615 (FF FF FF FF FF FF FF FF) tuples per table? ***
---------------------------------------------------------------------
state->state.del 8 00 00 00 00 00 00 00 01
*** Thats the number of tuples marked deleted. ***
---------------------------------------------------------------------
state->split 8 00 00 00 00 00 00 00 03
*** How many chunks are available due to the deletion of rows. But what is a chunk? ***
---------------------------------------------------------------------
state->dellink 8 00 00 00 00 00 00 00 07
*** Link to the a row marked deleted in the myd-file ***
---------------------------------------------------------------------
state->state.key_file_length 8 00 00 00 00 00 00 0c 00 2048
*** size of .MYI file --> the maximal size of an index file is 18446744073709551615
Bytes ***
---------------------------------------------------------------------
state->state.data_file_length 8 00 00 00 00 00 00 00 15
*** size of .MYD file --> the maximal size of an data file is 18446744073709551615
Bytes ***
---------------------------------------------------------------------
state->state.empty 8 00 00 00 00 00 00 00 00
*** I have got no idea what this value means ? ***
---------------------------------------------------------------------
state->state.key_empty 8 00 00 00 00 00 00 00 00
*** I have got no idea what this value means ? ***
---------------------------------------------------------------------
state->auto_increment 8 00 00 00 00 00 00 00 00
*** Current value of the autoincrement column --> only one auto_increment column
allowed ***
---------------------------------------------------------------------
state->checksum 8 00 00 00 00 00 00 00 00
*** Checksum for what??? ***
---------------------------------------------------------------------
state->process 4 00 00 09 E6
*** PID of the process that modified the table for the last time ***
---------------------------------------------------------------------
state->unique 4 00 00 00 0B
*** I assume, that this value is the number of unique entries in the index. But, if I have
a combined key (S2,S3) ... has the combination be unique in order to get counted??? In
other world, what does the 0x0B mean here??? *
---------------------------------------------------------------------
state->status 4 00 00 00 00
*** I do not have any idea ;-( ***
---------------------------------------------------------------------
state->update_count 4 00 00 00 04
*** Number of write locks to the table. What happens in case of an overflow? E.g. if I
Insert 0x01 00 00 00 00 rows, each with a separate insert statement? ***
---------------------------------------------------------------------
state->key_root 8 00 00 00 00 00 00 04 00
*** offset in myi-file where I1 key starts. But, what is the reference point for this
offset??? Furthermore, in the base part of the index you have got a field
base->keystart which contails the same value. Are both values the same? ***
---------------------------------------------------------------------
00 00 00 00 00 00 08 00
*** offset in myi-file where I2 key starts. But, what is the reference point for this
offset ... (2048 Bytes after what)? ***
---------------------------------------------------------------------
state->key_del 8 FF FF FF FF FF FF FF FF
*** Link to a place in the myi-file where a key was stored that was indexing a now deleted
tuple, Am I right? ***
---------------------------------------------------------------------
state->sec_index_changed 4 00 00 00 00
*** not used ... was it used in previous versions or will it be used in upcoming versions?
***
---------------------------------------------------------------------
state->sec_index_used 4 00 00 00 00
*** not used ... was it used in previous versions or will it be used in upcoming versions?
***
---------------------------------------------------------------------
state->version 4 3F 3F EB F7
*** this is called to be the timestamp of the creation of the index file, isn't it? ***
---------------------------------------------------------------------
state->key_map 8 00 00 00 03
*** "what keys are in use" --> but, what does this mean? Furthermore, I assume, that
the lenght in the documentation (8 bytes) is wrong here!***
---------------------------------------------------------------------
state->create_time 8 00 00 00 00 3F 3F EB F7
*** timestamp of the creation of the database. But, why do you use here 8 byte and for the
state->version only 4??? ***
---------------------------------------------------------------------
state->recover_time 8 00 00 00 00 00 00 00 00
*** timestamp of last recover ***
---------------------------------------------------------------------
state->check_time 8 00 00 00 00 3F 3F EB F7 "time of last check"
*** timestamp of last check ***
---------------------------------------------------------------------
state->rec_per_key_rows 8 00 00 00 00 00 00 00 00
*** I do not have any idea ;-( ***
---------------------------------------------------------------------
state->rec_per_key_parts 4 00 00 00 00 (key_parts = 3, so
00 00 00 00 rec_per_key_parts
00 00 00 00 occurs 3 times)
*** I do not have any idea ;-( ***
---------------------------------------------------------------------
