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DOCS-144 glossary revisions and post-review cleanup
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Sam Kleinman committed Mar 1, 2012
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143 changes: 67 additions & 76 deletions source/reference/glossary.rst
Expand Up @@ -299,11 +299,12 @@ Glossary

journal
A sequential, binary transaction used to bring the database into
a consistent state in the event of a hard shutdown. The journal is
enabled by default in MongoDB v2.0 and later. When enabled,
MongoDB writes data first to the journal and after to the core
data files. Journal commits are synced to disk every 100ms, but
this is configurable using the ``journalCommitInterval`` option.
a consistent state in the event of a hard shutdown. MongoDB
enables journaling by default for 64-bit builds of MongoDB
version 2.0 and later. When enabled, MongoDB writes data first
to the journal and after to the core data files. MongoDB commits
to the Journal every 100ms, but this is configurable using the
:setting:`journalCommitInterval` runtime option.

.. seealso:: The ":wiki:`Journaling`" wiki page.

Expand Down Expand Up @@ -340,21 +341,12 @@ Glossary

padding factor
An automatically-calibrated constant used to determine how much
extra space should be allocated per document container on disk.
extra space MongoDB should allocate per document container on disk.
A padding factor greater than 1 may allow a document to be rewritten
in-place if the document is ever enlarged by an update.


TODO: I don't believe that there's any reason to define lock in the abstract.

lock
An approach to concurrency where a single process or thread
prevents sibling process from accessing or changing a value
until the original process or thread has completed its
operation.
in-place if an update requires the document to grow.

read-lock
In the context of a reader-writer lock, a :term:`lock` that while
In the context of a reader-writer lock, a lock that while
held allows concurrent readers, but no writers.

config database
Expand All @@ -364,8 +356,8 @@ TODO: I don't believe that there's any reason to define lock in the abstract.
balancer
An internal MongoDB process that runs in the context of a
:term:`shard cluster` and manages the splitting and
migration of :term:`chunks <chunk>`. The balancer must
be disabled for all maintenance operations on a shard cluster.
migration of :term:`chunks <chunk>`. Administrators must disable
the balancer for all maintenance operations on a shard cluster.

fsync
An system call that flushes all dirty, in-memory pages to disk. MongoDB
Expand All @@ -375,7 +367,8 @@ TODO: I don't believe that there's any reason to define lock in the abstract.
In the context of a :term:`shard cluster`, a chunk is a contiguous
range of :term:`shard key` values assigned to a particular :term:`shard`.
By default, chunks are 64 megabytes or less. When they grow beyond the
configured chunk size, they are split in two.
configured chunk size, a :program:`mongos` splits the chunk into
two chunks.

geospatial
Data that relates to geographical location. In MongoDB, you may
Expand All @@ -396,11 +389,13 @@ TODO: I don't believe that there's any reason to define lock in the abstract.

.. code-block:: javascript
db.places.ensureIndex({position: "geoHaystack", type: 1})
db.places.ensureIndex( { position: "geoHaystack", type: 1 } )
You can then query on position and type:

db.places.find({position: [34.2, 33.3], type: "restaurant"})
.. code-block:: javascript
db.places.find( { position: [34.2, 33.3], type: "restaurant" } )
oplog
A :term:`capped collection` that stores an ordered history of
Expand All @@ -424,8 +419,6 @@ TODO: I don't believe that there's any reason to define lock in the abstract.
each running process. You can use a process's PID to inspect
a running process and send signals to it.

TODO: where is this even used in the docs?

JSONP
:term:`JSON` with Padding. Refers to a method of injecting JSON
into applications. Presents potential security concerns.
Expand All @@ -434,7 +427,7 @@ TODO: where is this even used in the docs?
An API design pattern centered around the idea of
resources and the CRUD operations that apply to them. Typically
implemented over HTTP. MongoDB provides a simple HTTP REST interface
that allows commands to be run against the server.
that allows HTTP clients to run commands against the server.

dbpath
Refers to the location of MongoDB's data file storage. The
Expand All @@ -447,17 +440,18 @@ TODO: where is this even used in the docs?
set name
In the context of a :term:`replica set`, the ``set name`` refers to
an arbitrary name given to a replica set when it's first configured.
All members of a replica set must have the same name, which is specified
using the ``--replSet`` flag on :program:`mongod`.
All members of a replica set must have the same name specified
with the :setting:`replSet` setting (or :option:`--replSet
<mongod --replSet>` option for :program:`mongod`.)

.. seealso:: :term:`replication`, ":doc:`/replication`" and
":doc:`/core/replication`."

_id
A field containing a unique ID, typically a BSON Object ID.
If not specified, this value is automatically assigned
when a new document is created. The ``_id`` field can
be thought of as a document's :term:`primary key`.
If not specified, this value is automatically assigned while
upon the creation of a new document. You can think of the
``_id`` as the document's :term:`primary key`.

lvm
Logical volume manager. LVM is a program that abstracts disk
Expand All @@ -475,8 +469,8 @@ TODO: where is this even used in the docs?
primary key
A record's unique, immutable identifier. In an RDBMS, the primary
key is typically an integer stored in each row's ``id`` field.
In MongoDB, a document's primary key is stored in a document's :term:`_id`
field and is usually a BSON Object ID.
In MongoDB, the :term:`_id` field holds a document's primary
key. Primary keys are usually :term:`BSON` Object IDs.

unique index
An index that enforces uniqueness for a particular field across
Expand All @@ -493,19 +487,21 @@ TODO: where is this even used in the docs?
profiler is most often used to diagnose slow queries.

shard key
In a sharded collection, a shard key is the field whose value
is used to distribute documents among members of the
In a sharded collection, a shard key is the field that MongoDB
uses to distribute documents among members of the
:term:`shard cluster`.

query
A read request. MongoDB queries use a :term:`JSON`-like
query language that includes a variety of :term:`database operators` whose names
begin with a ``$`` character. In the :program:`mongo` shell, you can issue queries
using the :func:`db.collection.find()` and :func:`db.collection.findOne()` methods.
A read request. MongoDB queries use a :term:`JSON`-like query
language that includes a variety of :term:`query operators <operator>`
with names that begin with a ``$`` character. In the
:program:`mongo` shell, you can issue queries using the
:func:`db.collection.find() <find>` and
:func:`db.collection.findOne() <findOne>` methods.

projection
A document given to a :term:`query` that specifies which fields
from the documents in the result set should be returned.
MongoDB will return from the documents in the result set.

pre-splitting
When deploying a :term:`shard cluster`, it is sometimes
Expand All @@ -531,7 +527,7 @@ TODO: where is this even used in the docs?
pipe
A communication channel UNIX allowing independent processes
to send and receive data. In the UNIX shell, piped operations
allow the output of one commmand to be passed as the input
allow users to direct the output of one command into the input
of another.

IPv6
Expand Down Expand Up @@ -559,48 +555,38 @@ TODO: where is this even used in the docs?
consistency and, therefore, does not provide multi-master replication.

rollback
A process that, in certain replica set situations, reverts writes opertaions
to ensure the consistency of all replica set members.

TODO: we need to rewrite the definitely completely. There are lots of
valid definitions, and it depends on the context.

consistency
The condition "up to date," and reliable quality of a database
system with multiple nodes and multiple instances of the same
data. A system may be ":term:`eventually consistent <eventual
consistency>`," with write or update operations returning
successfully before all copies of the data are in a consistent
state, or ":term:`strictly consistent <strict consistency>`,"
with no write or update operations returning before all copies of
the data are in a consistent state.
A process that, in certain replica set situations, reverts
writes operations to ensure the consistency of all replica set
members.

eventual consistency
A property of a distributed system allowing changes to the
system to propagate gradually. In a database system, this means
that readable nodes are not required to reflect the latest writes
at all times. In MongoDB, reads to a primary are consistent; reads
to secondary nodes are eventually consistent.
that readable nodes are not required to reflect the latest
writes at all times. In MongoDB, reads to a primary have
:term:`strict consistency`; reads to secondary nodes have
:term:`eventual consistency`.

strict consistency
A property of a distributed system requiring that all nodes always
reflect the latest changes to the system. In a database system, this means
that readable nodes are required to reflect the latest writes
at all times. In MongoDB, reads to a primary are consistent; reads
to secondary nodes are eventually consistent.
A property of a distributed system requiring that all nodes
always reflect the latest changes to the system. In a database
system, this means that any system that can provide data must
reflect the latest writes at all times. In MongoDB, reads to a
primary have :term:`strict consistency`; reads to secondary
nodes have :term:`eventual consistency`.

write concern
A setting on writes to MongoDB that allows the use to specify,
among other things, how far a write should be replicated
before returning.
how the database will handle a write operation before
retiring. This often determines how many :term:`replica set`
members should propagate a write before returning.

.. seealso:: ":ref:`Write Concern for Replica Sets
<replica-set-write-concern>`."
.. seealso:: ":ref:`Write Concern for Replica Sets <replica-set-write-concern>`."

priority
In the context of :term:`replica sets <replica set>`, priority
is a configurable values that help determine whih nodes in
a replica set are most likely to be elected: term:`primary`.
is a configurable values that help determine which nodes in
a replica set are most likely to become :term:`primary`.

.. seealso:: ":ref:`Replica Set Node Priority
<replica-set-node-priority>`"
Expand Down Expand Up @@ -640,10 +626,13 @@ valid definitions, and it depends on the context.
.. seealso:: ":ref:`Delayed Nodes <replica-set-delayed-members>`"

read preference
A setting on the MongoDB drivers that determines where reads
to any replica set, including shards, should be directed. By
default, reads are directed to primary nodes. However, you may
also direct reads to secondary nodes.
A setting on the MongoDB :doc:`drivers </applications/drivers>`
that determines where how the clients direct read
operations. Read preference affects all replica sets including
shards. By default, drivers direct all reads to :term:`primary`
nodes for :term:`strict consistency`. However, you may also
direct reads to secondary nodes for :term:`eventually consistent
<eventual consistency>` reads..

.. seealso:: ":ref:`Read Preference <replica-set-read-preference>`"

Expand Down Expand Up @@ -671,7 +660,7 @@ valid definitions, and it depends on the context.
.. seealso:: ":ref:`Replica Set Failover <replica-set-failover>`."

data-center awareness
A property that allows nodes in a system to be addressed
A property that allows clients to address nodes in a system to
based upon their location.

:term:`Replica sets <replica set>` implement data-center
Expand Down Expand Up @@ -767,5 +756,7 @@ valid definitions, and it depends on the context.
namespace.

replica pairs
The precursor to the MongoDB :term:`replica sets <replica set>`. Replica
pairs were deprecated in MongoDB v1.6.
The precursor to the MongoDB :term:`replica sets <replica
set>`.

.. deprecated:: 1.6

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