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Mnesia Release Notes

Dan Gudmundsson and Håkan Mattsson
04-08-22
AE notes_history.sgml

This document describes the changes made to the Mnesia system from version to version. The intention of this document is to list all incompatibilities as well as all enhancements and bugfixes for every release of Mnesia. Each release of Mnesia thus constitutes one section in this document. The title of each section is the version number of Mnesia.

## Mnesia 4.3.7

### Fixed Bugs and Malfunctions

Removed a memory leak on ram-only nodes, introduced in mnesia-4.3.6.

Own Id: OTP-6936 Aux Id: seq10786

### Known Bugs and Problems

Rearranging fragmented tables is an O(N^2) operation.

Own Id: OTP-6300

## Mnesia 4.3.6

### Fixed Bugs and Malfunctions

A bug causing lots of records to be lost at startup from an installed fallback has been fixed. The bug did however not show up when a backup file generated with mnesia:backup/1 or mnesia:backup_checkpoint/2 was installed as fallback. In order to trigger the bug, the items in the backup file had to be rearranged in such an order that records from different tables were interleaved with each other.

Own Id: OTP-6903 Aux Id: seq10763

Mnesia sometimes failed to commit schema operations on all nodes, this have been seen on smp machines but could happen on single processor as well with some bad timing.

Own Id: OTP-6904

mnesia:select/1 failed to return all matches on remote nodes if something was written to the table earlier in the same transaction.

Own Id: OTP-6908

### Known Bugs and Problems

Rearranging fragmented tables is an O(N^2) operation.

Own Id: OTP-6300

## Mnesia 4.3.5

### Fixed Bugs and Malfunctions

The internal index tables on bag tables where not always cleaned correctly. Thanks Christopher Faulet and Salazard Remy.

Own Id: OTP-6587

Changing the copy type with mnesia:change_table_copy/3 on a node which was down was not handled correctly, that caused an eternal table lock on the alive nodes. Thanks Hal Snyder.

Own Id: OTP-6709

### Known Bugs and Problems

Rearranging fragmented tables is an O(N^2) operation.

Own Id: OTP-6300

## Mnesia 4.3.4

### Fixed Bugs and Malfunctions

Adding fragments to ram_copies tables was allowed on nodes that where down.

Own Id: OTP-6367

Mnesia leaked transaction decisions (memory and disk space).

Own Id: OTP-6464

dirty_update_counter/3 did not work properly on disc tables when the counter was not initiated (Thanks to Sebastien Saint-Sevin).

Own Id: OTP-6545

Chunked mnesia:select on fragmented tables could crash (Thanks to Primanathan Reddy).

Own Id: OTP-6548

### Improvements and New Features

Introduced a new configure parameter dc_dump_limit.

Removed dead code (dialyzer warnings) and debugging features that called interpreter commands.

Minor performance increase when a lot of simultaneous transactions where active.

Thank you Scott Lystig Fritchie for debugging and bug reports.

Own Id: OTP-6478

### Known Bugs and Problems

Rearranging fragmented tables is an O(N^2) operation.

Own Id: OTP-6300

## Mnesia 4.3.3

### Fixed Bugs and Malfunctions

Mnesia could crash during startup when loading tables from remote node.

Own Id: OTP-6298 Aux Id: seq10402

Mnesia could fail to update all copies during del_table_copy.

Own Id: OTP-6299

### Known Bugs and Problems

Rearranging fragmented tables is an O(N^2) operation.

Own Id: OTP-6300

## Mnesia 4.3.2

### Fixed Bugs and Malfunctions

Mnesia sometimes failed to remove [d]ets table fixation, when using mnesia:first/1,mnesia:next/2 or qlc this could cause that deleted records are not actually deleted in the [d]ets table and that mnesia:[dirty_]first/1 reported the wrong key.

Own Id: OTP-6193 Aux Id: seq10376

## Mnesia 4.3.1

### Fixed Bugs and Malfunctions

Mnesia could crash (bad match in mnesia_controller) during start.

Own Id: OTP-6116 Aux Id: seq10305

## Mnesia 4.3

### Fixed Bugs and Malfunctions

Deleting tables during the start of mnesia on another node caused problems.

Own Id: OTP-5928 Aux Id: seq10111

Killing processes that runs nested transactions could crash mnesia.

Own Id: OTP-6027 Aux Id: seq10244

Creating or deleting tables with a checkpoint activated could crash mnesia

Own Id: OTP-6064

Table loading could be mixed with schema operations which could cause troubles.

Own Id: OTP-6065 Aux Id: seq10291

### Improvements and New Features

Added parallel table loaders to increase startup performance when the system have many small tables. The configuration variable no_table_loaders configures the number of loaders, default is two.

Own Id: OTP-6087