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Mnesia Release Notes

Dan Gudmundsson and Håkan Mattsson
05-01-26
AE notes.xml

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 4.4.15

### Improvements and New Features

Eliminated warnings for auto-imported BIF clashes.

Own Id: OTP-8840

## Mnesia 4.4.14

### Improvements and New Features

Added mnesia:subscribe(activity) contributed by Bernard Duggan.

Own Id: OTP-8519

## Mnesia 4.4.13

### Fixed Bugs and Malfunctions

Transactions could be left hanging if a node went down when invoking mnesia:sync_transaction/[1,2]. Thanks Igor Ribeiro Sucupira.

Own Id: OTP-8402

### Improvements and New Features

Igor Ribeiro Sucupira added the option to compress data when copying tables between Mnesia nodes.

Own Id: OTP-8406

## Mnesia 4.4.12

### Improvements and New Features

The documentation is now built with open source tools (xsltproc and fop) that exists on most platforms. One visible change is that the frames are removed.

Own Id: OTP-8250

## Mnesia 4.4.11

### Improvements and New Features

Fixed duplicate results with mnesia:index_read() on ordered_set tables. Reported by Sam Bobroff.

Fixed locking in mnesia:index_read() which now grabs a read table lock to ensure correctness, this may slow down the operation or block other processes trying to reach the same table.

Calling mnesia:dump_log() could crash mnesia, Reported by Igor Ribeiro Sucupira.

Own Id: OTP-8074

## Mnesia 4.4.10

### Fixed Bugs and Malfunctions

Mnesia crashed if a qlc query was running inside a transaction when mnesia stopped at another node. Thanks Teemu Antti-Poika.

Own Id: OTP-7968

Mnesia could crash when loading local_content tables.

Own Id: OTP-8002 Aux Id: seq11277

### Improvements and New Features

Minor (smp) optimizations.

Own Id: OTP-7928

## Mnesia 4.4.9

### Fixed Bugs and Malfunctions

mnesia:clear_table/1 crashed instead of returning {aborted,..} if it was called inside a transaction.

Own Id: OTP-7911

## Mnesia 4.4.8

### Fixed Bugs and Malfunctions

With bad timing several api functions could return or exit with a bad error message when mnesia was shutting down.

Own Id: OTP-7753 Aux Id: seq11179

mnesia:clear_table/1 cleared all nodes table content even if the table was local_content only type.

Own Id: OTP-7835

## Mnesia 4.4.7

### Fixed Bugs and Malfunctions

Disallowed match patterns ('_', and '$n') as argument to mnesia:delete_object/1 and friends.

Own Id: OTP-7524

### Improvements and New Features

Introduced a few new functions in Mnesia: mnesia:read/2, mnesia:first/3, mnesia:last/3, mnesia:prev/4, mnesia:next/4, mnesia_frag:first/1, mnesia_frag:last/1, mnesia_frag:prev/2, mnesia_frag:next/2.

Own Id: OTP-7625

## Mnesia 4.4.6

### Fixed Bugs and Malfunctions

mnesia:restore/2 aborted if a EXIT message appeared in the client message queue.

Own Id: OTP-7585 Aux Id: seq11046

## Mnesia 4.4.5

### Improvements and New Features

mnesia:clear_table/1 does not require that all replicas of the table are available anymore.

Own Id: OTP-7466 Aux Id: seq11015

## Mnesia 4.4.4

### Fixed Bugs and Malfunctions

Mnesia did not garbage collect transaction decisions on disk based nodes if no transactions where made on the local node.

Own Id: OTP-7419

## Mnesia 4.4.3

### Fixed Bugs and Malfunctions

Table referred to by foreign key did not have node_pool properly cleaned up when a node was removed from the schema. Thanks Paul Mineiro.

Own Id: OTP-7340

Mnesia crashed and generated a core dump if a schema_transaction was running when mnesia stopped.

Own Id: OTP-7378 Aux Id: seq10964

### Improvements and New Features

It is now possible to delete a db node even when other disk resident nodes are down. Thanks Paul Mineiro.

Own Id: OTP-7383

## Mnesia 4.4.2

### Fixed Bugs and Malfunctions

Sticky locks could lead to hanging transactions.

Own Id: OTP-7205 Aux Id: seq10793

mnesia:snmp_get_next_index/2 didn't work with partial index keys. Argument checking is now done according to documentation, in functions mnesia:snmp_get_row/2, mnesia:snmp_get_mnesia_key/2 and mnesia:snmp_get_next_index/2. These functions now require that RowIndex is a list.

*** POTENTIAL INCOMPATIBILITY ***

Own Id: OTP-7208

## Mnesia 4.4.1

### Fixed Bugs and Malfunctions

Snmp index tables was not initialized correctly in mnesia-4.4.

Own Id: OTP-7170 Aux Id: seq10870

### Known Bugs and Problems

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

Own Id: OTP-6300

## Mnesia 4.4

### Fixed Bugs and Malfunctions

Mnesia ignored the module argument to mnesia:restore/2. Thanks Paul Minerio.

Own Id: OTP-6981

### Improvements and New Features

Mnesia's snmp operations snmp_get_row/2, snmp_get_next_index/2 and snmp_get_mnesia_key/2 have been made context aware, i.e. inside a transaction they will compensate for table updates made in earlier in the same transaction. This might cause a performance drop if a lot of updates have been made before the invocation of these functions.

*** POTENTIAL INCOMPATIBILITY ***

Own Id: OTP-6856 Aux Id: seq10671

Introduced erlang:phash/2 as new default for fragmented tables. Already existing tables will continue to use whatever hash function they where using.

Own Id: OTP-6923

Introduced mnesia:is_transaction/0.

Own Id: OTP-6995 Aux Id: seq10812

### Known Bugs and Problems

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

Own Id: OTP-6300