[Maria-developers] More memory allocation for key seg
Hello Devlopers I was debugging the source code of mariadb. My query was MariaDB [sachin]> create table pro2(abc int primary key,xyz int , ass int ,unique(xyz,ass))engine=myisam; In table2myisam function of file ha_myisam.cc i found that we are allocating more memory for keysegments if (!(my_multi_malloc(MYF(MY_WME), recinfo_out, (share->fields * 2 + 2) * sizeof(MI_COLUMNDEF), keydef_out, share->keys * sizeof(MI_KEYDEF), &keyseg, (share->key_parts + share->keys) * sizeof(HA_KEYSEG), ^ here why this NullS))) And we donot use these extra key segments because suceeding for loop use only total number of share->key_parts keysegments. And same in ha_maria file.Is this a bug or I am missing something Regards sachin
Hi, Sachin! On Mar 22, Sachin Setia wrote:
Hello Devlopers I was debugging the source code of mariadb. My query was MariaDB [sachin]> create table pro2(abc int primary key,xyz int , ass int ,unique(xyz,ass))engine=myisam;
In table2myisam function of file ha_myisam.cc i found that we are allocating more memory for keysegments
if (!(my_multi_malloc(MYF(MY_WME), recinfo_out, (share->fields * 2 + 2) * sizeof(MI_COLUMNDEF), keydef_out, share->keys * sizeof(MI_KEYDEF), &keyseg, (share->key_parts + share->keys) * sizeof(HA_KEYSEG), ^ here why this NullS)))
And we donot use these extra key segments because suceeding for loop use only total number of share->key_parts keysegments. And same in ha_maria file.Is this a bug or I am missing something Regards sachin
The last key segment of every key is the row id. For dynamic row format it's the offset in the MYD file. For static row format (all rows have the same length as in your example above) it's the row number. Regards, Sergei Chief Architect MariaDB and security@mariadb.org
Thanks Sergei , this solved the mystery. Regards sachin On Wed, Mar 23, 2016 at 12:03 AM, Sergei Golubchik <serg@mariadb.org> wrote:
Hi, Sachin!
On Mar 22, Sachin Setia wrote:
Hello Devlopers I was debugging the source code of mariadb. My query was MariaDB [sachin]> create table pro2(abc int primary key,xyz int , ass int ,unique(xyz,ass))engine=myisam;
In table2myisam function of file ha_myisam.cc i found that we are allocating more memory for keysegments
if (!(my_multi_malloc(MYF(MY_WME), recinfo_out, (share->fields * 2 + 2) * sizeof(MI_COLUMNDEF), keydef_out, share->keys * sizeof(MI_KEYDEF), &keyseg, (share->key_parts + share->keys) * sizeof(HA_KEYSEG), ^ here why this NullS)))
And we donot use these extra key segments because suceeding for loop use only total number of share->key_parts keysegments. And same in ha_maria file.Is this a bug or I am missing something Regards sachin
The last key segment of every key is the row id. For dynamic row format it's the offset in the MYD file. For static row format (all rows have the same length as in your example above) it's the row number.
Regards, Sergei Chief Architect MariaDB and security@mariadb.org
participants (2)
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Sachin Setia -
Sergei Golubchik