Mysql – Calculate row size and max row size for a table

database-designinformation-schemainnodbMySQL

Problem:

Is there any way of calculating number of bytes occupied by the table creation, i know that you can get some information from information_schema.tables but that information is not accurate enough.

What actually required is the number of bytes according to the definition of the table for innodb only and collation could also be considered as utf-8-general-ci

For example a table test is as following

create table test
(
col1 varchar(25),
col2 int,
col3 varchar(3),
col4 char(15),
col5 datetime
);

Now would require to know the total row size that can be accumulated in one row according to the types of columns in the table.

Found a some sort of similar solution in MSSQL but need its MySQL version

Script to estimate row sizes for any table

Any help is much appreciated.

Best Answer

After much of thinking and researching found one answer which really helped in achieving what was required. It is a perl script and reference link is

http://dev.mysql.com/doc/refman/5.6/en/storage-requirements.html

#!/usr/bin/perl
use strict;
$| = 1;

my %DataType = (
"TINYINT"=>1, "SMALLINT"=>2, "MEDIUMINT"=>3, "INT"=>4, "INTEGER"=>4, "BIGINT"=>8,
"FLOAT"=>'$M<=24?4:8', "DOUBLE"=>8,
"DECIMAL"=>'int(($M-$D)/9)*4+int(((($M-$D)%9)+1)/2)+int($D/9)*4+int((($D%9)+1)/2)',
"NUMERIC"=>'int(($M-$D)/9)*4+int(((($M-$D)%9)+1)/2)+int($D/9)*4+int((($D%9)+1)/2)',
"BIT"=>'($M+7)>>3',
"DATE"=>3, "TIME"=>3, "DATETIME"=>8, "TIMESTAMP"=>4, "YEAR"=>1,
"BINARY"=>'$M',"CHAR"=>'$M*$CL',
"VARBINARY"=>'$M+($M>255?2:1)', "VARCHAR"=>'$M*$CL+($M>255?2:1)',
"ENUM"=>'$M>255?2:1', "SET"=>'($M+7)>>3',
"TINYBLOB"=>9, "TINYTEXT"=>9,
"BLOB"=>10, "TEXT"=>10,
"MEDIUMBLOB"=>11, "MEDIUMTEXT"=>11,
"LONGBLOB"=>12, "LONGTEXT"=>12
);

my %DataTypeMin = (
"VARBINARY"=>'($M>255?2:1)', "VARCHAR"=>'($M>255?2:1)'
);

my ($D, $M, $S, $C, $L, $dt, $dp ,$bc, $CL);
my $fieldCount = 0;
my $byteCount = 0;
my $byteCountMin = 0;
my @fields = ();
my $fieldName;
my $tableName;
my $defaultDbCL = 1;
my $defaultTableCL = 1;
my %charsetMaxLen;
my %collationMaxLen;

open (CHARSETS, "mysql -B --skip-column-names information_schema -e 'select CHARACTER_SET_NAME,MAXLEN from CHARACTER_SETS;' |");
%charsetMaxLen = map ( ( /^(\w+)/ => /(\d+)$/ ), <CHARSETS>);
close CHARSETS;

open (COLLATIONS, "mysql -B --skip-column-names information_schema -e 'select COLLATION_NAME,MAXLEN from CHARACTER_SETS INNER JOIN COLLATIONS USING(CHARACTER_SET_NAME);' |");
%collationMaxLen = map ( ( /^(\w+)/ => /(\d+)$/ ), <COLLATIONS>);
close COLLATIONS;

open (TABLEINFO, "mysqldump -d --compact ".join(" ",@ARGV)." |");

while (<TABLEINFO>) {
chomp;
if ( ($S,$C) = /create database.*?`([^`]+)`.*default\scharacter\sset\s+(\w+)/i ) {
$defaultDbCL = exists $charsetMaxLen{$C} ? $charsetMaxLen{$C} : 1;
print "Database: $S".($C?" DEFAULT":"").($C?" CHARSET $C":"")." (bytes per char: $defaultDbCL)\n\n";
next;
}
if ( /^create table\s+`([^`]+)`.*/i ) {
$tableName = $1;
@fields = ();
next;
}
if ( $tableName && (($C,$L) = /^\)(?:.*?default\scharset=(\w+))?(?:.*?collate=(\w+))?/i) ) {
$defaultTableCL = exists $charsetMaxLen{$C} ? $charsetMaxLen{$C} : (exists $collationMaxLen{$L} ? $collationMaxLen{$L} : $defaultDbCL);
print "Table: $tableName".($C||$L?" DEFAULT":"").($C?" CHARSET $C":"").($L?" COLLATION $L":"")." (bytes per char: $defaultTableCL)\n";
$tableName = "";
$fieldCount = 0;
$byteCount = 0;
$byteCountMin = 0;
while ($_ = shift @fields) {
if ( ($fieldName,$dt,$dp,$M,$D,$S,$C,$L) = /\s\s`([^`]+)`\s+([a-z]+)(\((\d+)(?:,(\d+))?\)|\((.*)\))?(?:.*?character\sset\s+(\w+))?(?:.*?collate\s+(\w+))?/i ) {
$dt = uc $dt;
if (exists $DataType{$dt}) {
if (length $S) {
$M = ($S =~ s/(\'.*?\'(?!\')(?=,|$))/$1/g);
$dp = "($M : $S)"
}
$D = 0 if !$D;
$CL = exists $charsetMaxLen{$C} ? $charsetMaxLen{$C} : (exists $collationMaxLen{$L} ? $collationMaxLen{$L} : $defaultTableCL);
$bc = eval($DataType{$dt});
$byteCount += $bc;
$byteCountMin += exists $DataTypeMin{$dt} ? $DataTypeMin{$dt} : $bc;
} else {
$bc = "??";
}
$fieldName.="\t" if length($fieldName) < 8;
print "bytes:\t".$bc."\t$fieldName\t$dt$dp".($C?" $C":"").($L?" COLL $L":"")."\n";
++$fieldCount;
}
}
print "total:\t$byteCount".($byteCountMin!=$byteCount?"\tleast: $byteCountMin":"\t\t")."\tcolumns: $fieldCount\n\n";
next;
}
push @fields, $_;
}
close TABLEINFO;

Thanks all for great help.

Related Solutions

Mysql – InnoDB create table error: “Row size too large”

The answers to your questions are complex, because they vary by InnoDB file format. Today, there are two formats, called Antelope and Barracuda.

The central tablespace file (ibdata1) is always in Antelope format. If you use file-per-table, you can make the individual files use Barracuda format by setting innodb_file_format=Barracuda in my.cnf.

Basic points:

One 16KB page of InnoDB data must hold at least two rows of data. Plus each page has a header and a footer containing page checksums and log sequence number and so on. That's where you get your limit of a bit less than 8KB per row.
Fixed-size data types like INTEGER, DATE, FLOAT, CHAR are stored on this primary data page and count toward the row size limit.
Variable-sized data types like VARCHAR, TEXT, BLOB are stored on overflow pages, so they don't count fully toward the row size limit. In Antelope, up to 768 bytes of such columns are stored on the primary data page in addition to being stored on the overflow page. Barracuda supports a dynamic row format, so it may store only a 20-byte pointer on the primary data page.
Variable-size data types are also prefixed with 1 or more bytes to encode the length. And InnoDB row format also has an array of field offsets. So there's an internal structure more or less documented in their wiki. [EDIT] Dead link - here looks better now.

Barracuda also supports a ROW_FORMAT=COMPRESSED to gain further storage efficiency for overflow data.

I also have to comment that I've never seen a well-designed table exceed the row size limit. It's a strong "code smell" that you're violating the repeating groups condition of First Normal Form.

Mysql – Store equations/formula in thesql db table

You can try to leverage dynamic SQL.

If you need to get a calculated value for an id

DELIMITER $$
CREATE PROCEDURE get_value(IN _id INT)
BEGIN
  SET @sql = NULL;

  SELECT CONCAT('SELECT ', formula, ' value FROM table1 WHERE id = ', 1)
    INTO @sql
    FROM table1
   WHERE id = 1;

  PREPARE stmt FROM @sql;
  EXECUTE stmt;
  DEALLOCATE PREPARE stmt;
  SET @sql = NULL;
END$$
DELIMITER ;

Note: You can of course use OUT parameter instead of returning the resultset if you want to.

Sample usage:

CALL get_value(1);

Sample output:

|           VALUE |
|-----------------|
| 82.916129032258 |

Here is how a procedure might look like to get all values calculated by formulas

DELIMITER $$
CREATE PROCEDURE get_values()
BEGIN
  SET @sql = NULL;

  SELECT GROUP_CONCAT(CONCAT(
    'SELECT id, ', formula, ' value FROM table1 WHERE id = ', id)
    ORDER BY id SEPARATOR ' UNION ALL ')
    INTO @sql
    FROM table1;

  PREPARE stmt FROM @sql;
  EXECUTE stmt;
  DEALLOCATE PREPARE stmt;
  SET @sql = NULL;
END$$
DELIMITER ;