makes search_related on extended rels without the optimized version work. involves...
[dbsrgits/DBIx-Class-Historic.git] / lib / DBIx / Class / Manual / Glossary.pod
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24105556 1=head1 NAME
2
880a1a0c 3DBIx::Class::Manual::Glossary - Clarification of terms used.
24105556 4
5=head1 INTRODUCTION
6
9e7b9292 7This document lists various terms used in DBIx::Class and attempts to
8explain them.
24105556 9
92fcfd01 10=head1 DBIx::Class TERMS
24105556 11
db2b2eb6 12=head2 DB schema
13
14Refers to a single physical schema within an RDBMS. Synonymous with the terms
15'database', for MySQL; and 'schema', for most other RDBMS(s).
16
17In other words, it's the 'xyz' _thing_ you're connecting to when using any of
18the following L<DSN|DBI/connect>(s):
19
20 dbi:DriverName:xyz@hostname:port
21 dbi:DriverName:database=xyz;host=hostname;port=port
22
9e7b9292 23=head2 Inflation
24
25The act of turning database row data into objects in
92fcfd01 26language-space. DBIx::Class result classes can be set up to inflate
27your data into perl objects which more usefully represent their
28contents. For example: L<DBIx::Class::InflateColumn::DateTime> for
29datetime or timestamp column data.
9e7b9292 30
92fcfd01 31See also L<DBIx::Class::InflateColumn>.
9e7b9292 32
92fcfd01 33=head2 Deflation
9e7b9292 34
92fcfd01 35The opposite of L</Inflation>. Existing perl objects that represent
36column values can be passed to DBIx::Class methods to store into the
37database. For example a L<DateTime> object can be automatically
38deflated into a datetime string for insertion.
9e7b9292 39
92fcfd01 40See L<DBIx::Class::InflateColumn> and other modules in that namespace.
9e7b9292 41
24105556 42=head2 ORM
43
9e7b9292 44Object-relational mapping, or Object-relationship modelling. Either
45way it's a method of mapping the contents of database tables (rows),
46to objects in programming-language-space. DBIx::Class is an ORM.
47
7cf4ae7a 48=head2 Relationship
49
50In DBIx::Class a relationship defines the connection between exactly
51two tables. The relationship condition lists the columns in each table
52that contain the same values. It is used to output an SQL JOIN
53condition between the tables.
54
55=head2 Relationship bridge
56
57A relationship bridge, such as C<many_to_many> defines an accessor to
92fcfd01 58retrieve row contents across multiple relationships.
7cf4ae7a 59
92fcfd01 60The difference between a bridge and a relationship is, that the bridge
61cannot be used to C<join> tables in a C<search>, instead its component
62relationships must be used.
24105556 63
92fcfd01 64=head2 Schema
24105556 65
92fcfd01 66A Schema object represents your entire table collection, plus the
67connection to the database. You can create one or more schema objects,
68connected to various databases, with various users, using the same set
69of table L</Result class> definitions.
70
71At least one L<DBIx::Class::Schema> class is needed per database.
72
73=head2 Result class
74
75A Result class defines both a source of data (usually one per table),
76and the methods that will be available in the L</Row> objects created
77using that source.
78
79One Result class is needed per data source (table, view, query) used
80in your application, they should inherit from L<DBIx::Class::Core>.
24105556 81
82=head2 ResultSource
83
92fcfd01 84ResultSource objects represent the source of your data, these are
85sometimes (incorrectly) called table objects.
86
87ResultSources do not need to be directly created, a ResultSource
88instance is created for each L</Result class> in your L</Schema>, by
89the proxied methods C<table> and C<add_columns>.
24105556 90
91See also: L<DBIx::Class::ResultSource/METHODS>
92
92fcfd01 93=head2 ResultSet
94
95This is an object representing a set of conditions to filter data. It
96can either be an entire table, or the results of a query. The actual
97data is not held in the ResultSet, it is only a description of how to
98fetch the data.
99
100See also: L<DBIx::Class::ResultSet/METHODS>
101
24105556 102=head2 Record
103
104See Row.
105
106=head2 Row
107
108Row objects contain your actual data. They are returned from ResultSet objects.
109
110=head2 Object
111
112See Row.
113
92fcfd01 114=head2 join
24105556 115
92fcfd01 116=head2 prefetch
117
118
119=head1 SQL TERMS
120
121=head2 Join
122
123This is an SQL keyword, it is used to link multiple tables in one SQL
124statement. This enables us to fetch data from more than one table at
125once, or filter data based on content in another table, without having
126to issue multiple SQL queries.
127
128=head2 Normalisation
129
130A normalised database is a sane database. Each table contains only
131data belonging to one concept, related tables refer to the key field
132or fields of each other. Some links to webpages about normalisation
133can be found in L<DBIx::Class::Manual::FAQ|the FAQ>.
134
135=head2 Related data
136
137In SQL, related data actually refers to data that are normalised into
138the same table. (Yes. DBIC does mis-use this term).