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Showing entries 1 to 10 of 10

Displaying posts with tag: frm (reset)

Some current MySQL Architecture writings
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So, I’ve been looking around for a while (and a few times now) for any good resources that cover a bunch of MySQL architecture and technical details aimed towards the technically proficient but not MySQL literate audience. I haven’t really found anything. I mean, there’s the (huge and very detailed) MySQL manual, there’s the MySQL Internals manual (which is sometimes only 10 years out of date) and there’s various blog entries around the place. So I thought I’d write something explaining roughly how it all …

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Past, Present and future of MySQL and variants Part 1: Ghosts of MySQL Past
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You can watch the video of my 2014 talk here:

But let’s talk about things in blog form rather than video form :)

Back in 1979, there was UNIREG. A text UI to records (rows) in a …

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Understanding the maximum number of columns in a MySQL table
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This post was initially going to be two sets of polls: “What is the maximum number of columns in MySQL?” and “What is the minimum maximum number of columns in MySQL?”. Before you read on, ponder those questions and come up with your own answers… and see if you’re right or can prove me wrong!

Back in 2009, I finished what seemed an epic task in the Drizzle code base: banishing the FRM file. Why? We felt it was not a good idea to keep arbitrary and obscure limitations from the 1980s alive in the …

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Things I’ve done in Drizzle
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When writing my Dropping ACID: Eating Data in a Web 2.0 Cloud World talk for LCA2011 I came to the realisation that I had forgotten a lot of the things I had worked on in MySQL and MySQL Cluster. So, as a bit of a retrospective as part of the Drizzle7 GA release, I thought I might try and write down a (incomplete) list of the various things I’ve worked on in Drizzle.

I noticed I did a lot of code removal, that’s all fine and dandy but maybe I won’t list all of that… except perhaps my first branch that was merged :)


  • First ever branch that was merged: some …
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ENUM now works properly (in Drizzle)
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Over at the Drizzle blog, the recent 2010-06-07 tarball was announced. This tarball release has my fixes for the ENUM type, so that it now works as it should. I was quite amazed that such a small block of code could have so many bugs! One of the most interesting was the documented limit we inherited from MySQL (see the MySQL Docs on ENUM) of a maximum of 65,535 elements for an ENUM column.

This all …

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The Table protobuf message format
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If you’ve ever opened up drizzled/message/table.proto in the Drizzle source tree you will have seen what’s in the table message: the structure that describes a database table in Drizzle. Previously I’ve talked about the Table message more generally, giving a fair bit of history of the FRM …

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Drizzle FRM replacement: the table proto
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Drizzle originally inherited the FRM file from MySQL (which inherited it from UNIREG). The FRM file stores metadata about a table; what columns it has, what type those columns are, what indexes, any default values, comments etc are all stored in the FRM. In the days of MyISAM, this worked relatively well. The row data was stored in table.MYD, indexes on top of it in table.MYI and information about the format of the row was
in table.FRM. Since MyISAM itself wasn’t crash safe, it didn’t really matter if creating/deleting the FRM file along with the table was either.

As more sophisticated engines were introduced (e.g. InnoDB) …

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No implicit defaults
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See also: MySQL Bug 43151

The MySQL Manual proudly states that you don’t get implicit default values if strict mode.

mysql> set sql_mode='STRICT_ALL_TABLES';
Query OK, 0 rows affected (0.00 sec)

mysql> create table t1 (a int, b int, c int, d int, e int, f int, g int, h int,i int,
primary key (a,b,c,d,e,f,g,i,h)) engine=MyISAM;
Query OK, 0 rows affected (0.03 sec)

mysql> show create table t1\G
*************************** 1. row ***************************
       Table: t1
Create …
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The FRM file format
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It’s fortunate that I’m watching Veronica Mars again with a mate; a more-than-you-think amount of detective work is required to understand the relationship (and format) of the TABLE_SHARE, the FRM file and HA_CREATE_INFO. Oh, also you’ll need drizzled/base.h and drizzled/structs.h and drizzled/table_share.h is also a good one to have open.

The FRM file is really a FoRM file from UNIREG (see copies of really old mysql docs around the place or even better, the links off …

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Progress in nofrm branch
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“Ban FRM Now!” branch in Launchpad

Now we’re reading part of the table information out of the proto file on disk instead of the frm.

Not everything (yet) but a bit. Good first steps. Had to fix bugs along the way as well (and find weirdness in FRM file format…).

Progress is being made.

Showing entries 1 to 10 of 10

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