InnoDB Page Compression

MariaDB starting with 10.1

InnoDB Page Compression was added in MariaDB 10.1.0. Support for the snappy compression algorithm was added in MariaDB 10.1.3.

Overview

InnoDB page compression provides a way to compress InnoDB tables.

Use Cases

  • InnoDB page compression can be used on any storage device and any file system.
  • InnoDB page compression is most beneficial on solid state drives (SSDs) and other flash storage. See Optimized for Flash Storage for more information.

Differences Compared to the COMPRESSED Row Format

InnoDB page compression is a modern way to compress your InnoDB tables. It is similar to InnoDB's COMPRESSED row format, but it has many advantages. Some of the differences are:

  • With InnoDB page compression, compressed pages are immediately decompressed after being read from the tablespace file, and only uncompressed pages are stored in the buffer pool. In contrast, with InnoDB's COMPRESSED row format, compressed pages are decompressed immediately after they are read from the tablespace file, and both the uncompressed and compressed pages are stored in the buffer pool. This means that the COMPRESSED row format uses more space in the buffer pool than InnoDB page compression does.
  • With InnoDB page compression, pages are compressed just before being written to the tablespace file. In contrast, with InnoDB's COMPRESSED row format, pages are re-compressed immediately after any changes, and the compressed pages are stored in the buffer pool alongside the uncompressed pages. These changes are then occasionally flushed to disk. This means that the COMPRESSED row format re-compresses data more frequently than InnoDB page compression does.
  • With InnoDB page compression, multiple compression algorithms are supported. In contrast, with InnoDB's COMPRESSED row format, zlib is the only supported compression algorithm. This means that the COMPRESSED row format has less compression options than InnoDB page compression does.

In general, InnoDB page compression is superior to the COMPRESSED row format.

Configuring the InnoDB Page Compression Algorithm

There is not currently a table option to set different InnoDB page compression algorithms for individual tables.

However, the server-wide InnoDB page compression algorithm can be configured by setting the innodb_compression_algorithm system variable.

When this system variable is changed, the InnoDB page compression algorithm does not change for existing pages that were already compressed with a different InnoDB page compression algorithm. InnoDB is able to handle this situation without issues, because every page in an InnoDB tablespace contains metadata about the InnoDB page compression algorithm in the page header. This means that InnoDB supports having uncompressed pages and pages compressed with different InnoDB page compression algorithms in the same InnoDB tablespace at the same time.

This system variable can be set to one of the following values:

System Variable ValueDescription
nonePages are not compressed. This is the default value in MariaDB 10.2.3 and before, and MariaDB 10.1.21 and before.
zlibPages are compressed using the bundled zlib compression algorithm. This is the default value in MariaDB 10.2.4 and later, and MariaDB 10.1.22 and later.
lz4Pages are compressed using the lz4 compression algorithm.
lzoPages are compressed using the lzo compression algorithm.
lzmaPages are compressed using the lzma compression algorithm.
bzip2Pages are compressed using the bzip2 compression algorithm.
snappyPages are compressed using the snappy algorithm.

However, on many distributions, the standard MariaDB builds do not support all InnoDB page compression algorithms by default.

This system variable can be changed dynamically with SET GLOBAL. For example:

SET GLOBAL innodb_compression_algorithm='lzma';

This system variable can also be set in a server option group in an option file prior to starting up the server. For example:

[mariadb]
...
innodb_compression_algorithm=lzma

Checking Supported InnoDB Page Compression Algorithms

On many distributions, the standard MariaDB builds do not support all InnoDB page compression algorithms by default. Therefore, if you want to use a specific InnoDB page compression algorithm, then you should check whether your MariaDB build supports it.

The zlib compression algorithm is always supported.

A MariaDB build's support for other InnoDB page compression algorithms can be checked by querying the following status variables with SHOW GLOBAL STATUS:

Status VariableDescription
Innodb_have_lz4Whether InnoDB supports the lz4 compression algorithm.
Innodb_have_lzoWhether InnoDB supports the lzo compression algorithm.
Innodb_have_lzmaWhether InnoDB supports the lzma compression algorithm.
Innodb_have_bzip2Whether InnoDB supports the bzip2 compression algorithm.
Innodb_have_snappyWhether InnoDB supports the snappy compression algorithm.

For example:

SHOW GLOBAL STATUS WHERE Variable_name IN (
   'Innodb_have_lz4', 
   'Innodb_have_lzo', 
   'Innodb_have_lzma', 
   'Innodb_have_bzip2', 
   'Innodb_have_snappy'
);
+--------------------+-------+
| Variable_name      | Value |
+--------------------+-------+
| Innodb_have_lz4    | OFF   |
| Innodb_have_lzo    | OFF   |
| Innodb_have_lzma   | ON    |
| Innodb_have_bzip2  | OFF   |
| Innodb_have_snappy | OFF   |
+--------------------+-------+
5 rows in set (0.001 sec)

Adding Support for an InnoDB Page Compression Algorithm

On many distributions, the standard MariaDB builds do not support all InnoDB page compression algorithms by default. Therefore, if you want to use certain InnoDB page compression algorithms, then you may need to do the following:

  • Download the package for the desired compression library from the above links.
  • Install the package for the desired compression library.
  • Compile MariaDB from the source distribution.

The general steps for compiling MariaDB are:

  • Download and unpack the source code distribution:
wget https://downloads.mariadb.com/MariaDB/mariadb-10.4.8/source/mariadb-10.4.8.tar.gz
tar -xvzf mariadb-10.4.8.tar.gz
cd mariadb-10.4.8/
  • Configure the build using cmake:
cmake .
  • Check CMakeCache.txt to confirm that it has found the desired compression library on your system.
  • Compile the build:
make
  • Either install the build:
make install

Or make a package to install:

make package

See Compiling MariaDB From Source for more information.

Enabling InnoDB Page Compression

InnoDB page compression is not enabled by default. However, InnoDB page compression can be enabled for just individual InnoDB tables or it can be enabled for all new InnoDB tables by default.

InnoDB page compression is also only supported if the InnoDB table is in a file per-table tablespace. Therefore, the innodb_file_per_table system variable must be set to ON to use InnoDB page compression.

InnoDB page compression is only supported if the InnoDB table uses the Barracuda file format.Therefore, in MariaDB 10.1 and before, the innodb_file_format system variable must be set to Barracuda to use InnoDB page compression.

InnoDB page compression is also only supported if the InnoDB table's row format is COMPACT or DYNAMIC.

Enabling InnoDB Page Compression by Default

MariaDB starting with 10.2.3

The innodb_compression_default system variable was first added in MariaDB 10.2.3.

In MariaDB 10.2.3 and later, InnoDB page compression can be enabled for all new InnoDB tables by default by setting the innodb_compression_default system variable to ON.

This system variable can be set to one of the following values:

System Variable ValueDescription
OFFNew InnoDB tables do not use InnoDB page compression. This is the default value.
ONNew InnoDB tables use InnoDB page compression.

This system variable can be changed dynamically with SET GLOBAL. For example:

SET GLOBAL innodb_compression_default=ON;

This system variable's session value can be changed dynamically with SET SESSION. For example:

SET GLOBAL innodb_file_per_table=ON;

SET GLOBAL innodb_file_format='Barracuda';

SET GLOBAL innodb_default_row_format='dynamic';

SET GLOBAL innodb_compression_algorithm='lzma';

SET SESSION  innodb_compression_default=ON;

CREATE TABLE users (
   user_id int not null, 
   b varchar(200), 
   primary key(user_id)
) 
   ENGINE=InnoDB;

This system variable can also be set in a server option group in an option file prior to starting up the server. For example:

[mariadb]
...
innodb_compression_default=ON

Enabling InnoDB Page Compression for Individual Tables

InnoDB page compression can be enabled for individual tables by setting the PAGE_COMPRESSED table option to 1. For example:

SET GLOBAL innodb_file_per_table=ON;

SET GLOBAL innodb_file_format='Barracuda';

SET GLOBAL innodb_default_row_format='dynamic';

SET GLOBAL innodb_compression_algorithm='lzma';

CREATE TABLE users (
   user_id int not null, 
   b varchar(200), 
   primary key(user_id)
) 
   ENGINE=InnoDB
   PAGE_COMPRESSED=1;

Configuring the Compression Level

Some InnoDB page compression algorithms support a compression level option, which configures how the InnoDB page compression algorithm will balance speed and compression.

The compression level's supported values range from 1 to 9. The range goes from the fastest to the most compact, which means that 1 is the fastest and 9 is the most compact.

Only the following InnoDB page compression algorithms currently support compression levels:

If an InnoDB page compression algorithm does not support compression levels, then it ignores any provided compression level value.

Configuring the Default Compression Level

The default compression level can be configured by setting the innodb_compression_level system variable.

This system variable's default value is 6.

This system variable can be changed dynamically with SET GLOBAL. For example:

SET GLOBAL innodb_compression_level=9;

This system variable can also be set in a server option group in an option file prior to starting up the server. For example:

[mariadb]
...
innodb_compression_level=9

Configuring the Compression Level for Individual Tables

The compression level for individual tables can also be configured by setting the PAGE_COMPRESSION_LEVEL table option for the table. For example:

SET GLOBAL innodb_file_per_table=ON;

SET GLOBAL innodb_file_format='Barracuda';

SET GLOBAL innodb_default_row_format='dynamic';

SET GLOBAL innodb_compression_algorithm='lzma';

CREATE TABLE users (
   user_id int not null, 
   b varchar(200), 
   primary key(user_id)
) 
   ENGINE=InnoDB
   PAGE_COMPRESSED=1
   PAGE_COMPRESSION_LEVEL=9;

Configuring the Failure Threshold and Maximum Padding

InnoDB page compression can encounter compression failures.

InnoDB page compression's failure threshold can be configured. If InnoDB encounters more compression failures than the failure threshold, then it pads pages with zeroed out bytes before attempting to compress them as a way to reduce failures. If the failure rate stays above the failure threshold, then InnoDB pads pages with more zeroed out bytes in 128 byte increments.

InnoDB page compression's maximum padding can also be configured.

Configuring the Failure Threshold

The failure threshold can be configured by setting the innodb_compression_failure_threshold_pct system variable.

This system variable's supported values range from 0 to 100.

This system variable's default value is 5.

This system variable can be changed dynamically with SET GLOBAL. For example:

SET GLOBAL innodb_compression_failure_threshold_pct=10;

This system variable can also be set in a server option group in an option file prior to starting up the server. For example:

[mariadb]
...
innodb_compression_failure_threshold_pct=10

Configuring the Maximum Padding

The maximum padding can be configured by setting the innodb_compression_pad_pct_max system variable.

This system variable's supported values range from 0 to 75.

This system variable's default value is 50.

This system variable can be changed dynamically with SET GLOBAL. For example:

SET GLOBAL innodb_compression_pad_pct_max=75;

This system variable can also be set in a server option group in an option file prior to starting up the server. For example:

[mariadb]
...
innodb_compression_pad_pct_max=75

Saving Storage Space with Sparse Files

When InnoDB page compression is used, InnoDB may still write the compressed page to the tablespace file with the original size of the uncompressed page, which would be equivalent to the value of the innodb_page_size system variable. This is done by design, because when InnoDB's I/O code needs to read the page from disk, it can only read the full page size. However, this is obviously not optimal.

On file systems that support sparse files, this problem is solved by writing the tablespace file as a sparse file using the punch hole technique. With the punch hole technique, InnoDB will only write the actual compressed page size to the tablespace file, aligned to sector size. The rest of the page is trimmed.

This punch hole technique allows InnoDB to read the compressed page from disk as the full page size, even though the compressed page really takes up less space on the file system.

There are some potential disadvantages to using sparse files:

  • Some utilities may require special options in order to handle sparse files in an efficient manner.
  • Most existing file systems are slow to unlink() sparse files. As a consequence, if a tablespace file is a sparse file, then dropping the table can be very slow.

Sparse File Support on Linux

On Linux, the following file systems support sparse files:

  • ext3
  • ext4
  • xfs
  • btrfs
  • nvmfs

On Linux, file systems need to support the fallocate() system call with the FALLOC_FL_PUNCH_HOLE and FALLOC_FL_KEEP_SIZE flags. For example:

fallocate(file_handle, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, file_offset, remainder_len);

Some Linux utilities may require special options in order to work with sparse files efficiently. For example:

  • The ls utility will report the non-sparse size of the tablespace file when executed with default behavior, but ls -s will report the actual amount of storage allocated for the tablespace file.
  • The cp utility is pretty good at auto-detecting sparse files, but it also provides the cp --sparse=always and cp --sparse=never options, if the auto-detection is not desired.
  • The tar utility will archive sparse files with their non-sparse size when executed with default behavior, but tar --sparse will auto-detect sparse files, and archive them with their sparse size.

Sparse File Support on Windows

On Windows, the following file systems support sparse files:

  • NTFS

On Windows, file systems need to support the DeviceIoControl() function with the FSCTL_SET_SPARSE and FSCTL_SET_ZERO_DATA control codes. For example:

DeviceIoControl(file_handle, FSCTL_SET_SPARSE, inbuf, inbuf_size, 
   outbuf, outbuf_size,  NULL, &overlapped)
...
DeviceIoControl(file_handle, FSCTL_SET_ZERO_DATA, inbuf, inbuf_size, 
   outbuf, outbuf_size,  NULL, &overlapped)

Configuring InnoDB to use Sparse Files

In MariaDB 10.3 and later, InnoDB uses the punch hole technique to create sparse files used automatically when the underlying file system supports sparse files.

In MariaDB 10.2 and before, InnoDB can be configured to use the punch hole technique to create sparse files by configuring the innodb_use_trim and innodb_use_fallocate system variables. These system variables can be set in a server option group in an option file prior to starting up the server. For example:

[mariadb]
...
innodb_use_trim=ON
innodb_use_fallocate=ON

Optimized for Flash Storage

InnoDB page compression was designed to be optimized on solid state drives (SSDs) and other flash storage.

InnoDB page compression was originally developed by collaborating with Fusion-io. As a consequence, it was originally designed to work best on FusionIO devices using NVMFS. Fusion-io has since been acquired by Western Digital, and they have decided not to continue supporting NVMFS.

However, InnoDB page compression is still likely to be most optimized on solid state drives (SSDs) and other flash storage.

InnoDB page compression works without any issues on hard disk drives (HDDs). However, since its compression relies on the use of sparse files, the data may be somewhat fragmented on disk. This fragmentation may hurt performance on HDDs, since they handle random reads and writes much more slowly than flash storage.

Configuring InnoDB Page Flushing

With InnoDB page compression, pages are compressed when they are flushed to disk. Therefore, it can be helpful to optimize the configuration of InnoDB's page flushing. See InnoDB Page Flushing for more information.

Monitoring InnoDB Page Compression

InnoDB page compression can be monitored by querying the following status variables with SHOW GLOBAL STATUS:

Status VariableDescription
Innodb_page_compression_savedBytes saved by compression
Innodb_page_compression_trim_sect512Number of 512 sectors trimmed
Innodb_page_compression_trim_sect1024Number of 1024 sectors trimmed
Innodb_page_compression_trim_sect2048Number of 2048 sectors trimmed
Innodb_page_compression_trim_sect4096Number of 4096 sectors trimmed
Innodb_page_compression_trim_sect8192Number of 8192 sectors trimmed
Innodb_page_compression_trim_sect16384Number of 16384 sectors trimmed
Innodb_page_compression_trim_sect32768Number of 32768 sectors trimmed
Innodb_num_pages_page_compressedNumber of pages compressed
Innodb_num_page_compressed_trim_opNumber of trim operations
Innodb_num_page_compressed_trim_op_savedNumber of trim operations saved
Innodb_num_pages_page_decompressedNumber of pages decompressed
Innodb_num_pages_page_compression_errorNumber of compression errors

With InnoDB page compression, a page is only compressed when it is flushed to disk. This means that if you are monitoring InnoDB page compression via these status variables, then the status variables values will only get incremented when the dirty pages are flushed to disk, which does not necessarily happen immediately. For example:

CREATE TABLE `tab` (
     `id` int(11) NOT NULL,
     `str` varchar(50) DEFAULT NULL,
     PRIMARY KEY (`id`)
   ) ENGINE=InnoDB;
 
INSERT INTO tab VALUES (1, 'str1');

SHOW GLOBAL STATUS LIKE 'Innodb_num_pages_page_compressed';
+----------------------------------+-------+
| Variable_name                    | Value |
+----------------------------------+-------+
| Innodb_num_pages_page_compressed | 0     |
+----------------------------------+-------+
 
SET GLOBAL innodb_file_per_table=ON;

SET GLOBAL innodb_file_format='Barracuda';

SET GLOBAL innodb_default_row_format='dynamic';

SET GLOBAL innodb_compression_algorithm='lzma';
 
ALTER TABLE tab PAGE_COMPRESSED=1;

SHOW GLOBAL STATUS LIKE 'Innodb_num_pages_page_compressed';
+----------------------------------+-------+
| Variable_name                    | Value |
+----------------------------------+-------+
| Innodb_num_pages_page_compressed | 0     |
+----------------------------------+-------+
 
SELECT SLEEP(10);
+-----------+
| SLEEP(10) |
+-----------+
|         0 |
+-----------+
 
SHOW GLOBAL STATUS LIKE 'Innodb_num_pages_page_compressed';
+----------------------------------+-------+
| Variable_name                    | Value |
+----------------------------------+-------+
| Innodb_num_pages_page_compressed | 3     |
+----------------------------------+-------+

Compatibility with Backup Tools

Mariabackup supports InnoDB page compression.

Percona XtraBackup does not support InnoDB page compression.

Acknowledgements

  • InnoDB page compression was developed by collaborating with Fusion-io. Special thanks especially to Dhananjoy Das and Torben Mathiasen.

See Also

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