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Alzabo::Runtime::Table - Table objects |
Alzabo::Runtime::Row objectAlzabo::Runtime::RowCursor objectAlzabo::Runtime::Column object)Alzabo::Runtime::Table object)Alzabo::Runtime::Column object)Alzabo::Column objects)Alzabo::Column objects)
Alzabo::Runtime::Table - Table objects
my $table = $schema->table('foo');
my $row = $table->row_by_pk( pk => 1 );
my $row_cursor = $table->rows_where( where => [ C<Alzabo::Column> object, '=', 5 } );
This object is able to create rows, either by making objects based on existing data or inserting new data to make new rows.
This object also implements a method of lazy column evaluation that can be used to save memory and database wear and tear, though it needs to be used carefully. Please see methods as well as LAZY COLUMN LOADING for details.
Alzabo::Table
Note: all relevant documentation from the superclass has been merged into this document.
Alzabo::Runtime::Row object
Inserts the given values into the table. If no values are given for a primary key column and the column is sequenced then the values will be generated from the sequence.
All other parameters given will be passed directly to the
Alzabo::Runtime::Row->new method
(such as the no_cache parameter).
A new Alzabo::Runtime::Row object.
The primary key can be either a simple scalar, as when the table has a single primary key, or a hash reference of column names to primary key values when the primary key is more than one column.
All other parameters given will be passed directly to the
Alzabo::Runtime::Row->new
method (such as the no_cache parameter).
A new Alzabo::Runtime::Row object. If no
rows in the database match the value(s) given then an empty list or
undef will be returned (for list or scalar context).
This method is useful for regenerating a row that has been saved by
reference to its id (returned by the
Alzabo::Runtime::Row->id method).
This may be more convenient than saving a multi-column primary key
when trying to maintain state in a web app, for example.
A string representation of a row's id (as returned by the
Alzabo::Runtime::Row->id method).
All other parameters given will be passed directly to the
Alzabo::Runtime::Row->new
method (such as the no_cache parameter).
A new Alzabo::Runtime::Row object. If no
rows in the database match the value(s) given then an empty list or
undef will be returned (for list or scalar context).
Alzabo::Runtime::RowCursor objectThe following methods all return an
Alzabo::Runtime::RowCursor object
representing the results of the query. This is the case even for
queries that end up returning one or zero rows.
These three methods all take the following parameters in addition to whatever is described:
order_by => { columns => $column_object or \@column_objects,
sort => 'ASC' or 'DESC' }
A simple way to retrieve a row cursor based on one or more colum values. This does not handle any conditionals besides equality.
Alzabo::Column object or SQL function, $comparison, $value or Alzabo::Column object ]$comparison should be a string
containing a SQL operator such as '>' or '='.
The parameter can also be an array of references to such arrays:
[ [ C<Alzabo::Column> object or SQL function, $comparison, $value or C<Alzabo::Column> object ], [ C<Alzabo::Column> object or SQL function, $comparison, $value or C<Alzabo::Column> object ] ]
For more details on exactly what the possibilities are here, please see the documentation for Alzabo::SQLMaker.
By default, each clause represented by an array reference is joined together with an 'AND'. However, you can put the string 'or' between two array references to cause them to be joined with an 'OR', such as:
[ [ $foo_col, '=', 5 ], 'or', [ $foo_col, '>', 10 ] ]
which would generate SQL something like:
WHERE foo = 5 OR foo > 10
If you want to be explicit, you can also use the string 'and'.
If you need to group conditionals you can use '(' and ')' characters in between array references representing a conditional. For example:
[ [ $foo_col, '=', 5 ],
'(',
[ $foo_col, '>', 10 ]
'or',
[ $bar_col, '<', 50, ')' ],
')' ]
which would generate SQL something like:
WHERE foo = 5 AND ( foo > 10 OR bar < 50 )
Make sure that your parentheses balance out or an exception will be thrown.
You can also use the SQL functions (Using SQL Functions in the Alzabo manpage) exported from the SQLMaker subclass you are using. For example:
[ LENGTH($foo_col), '<', 10 ]
would generate something like:
WHERE LENGTH(foo) < 10
All other parameters given will be passed directly to the
Alzabo::Runtime::Row->new
method (such as the no_cache parameter).
Given these items this method generates SQL that will retrieve a set of primary keys for the table.
An Alzabo::Runtime::RowCursor object
representing the query.
Simply returns all the rows in the table.
All parameters given will be passed directly to the
Alzabo::Runtime::Row->new method
(such as the no_cache parameter).
An Alzabo::Runtime::RowCursor object
representing the query.
A scalar indicating how many rows the table has.
Alzabo::Column objects ]
$table->function( select => [ $table->column('name'), COUNT( $table->column('name') ) ] );
group_by => { columns => $column_object or \@column_objects,
sort => 'ASC' or 'DESC' }
This method is used to call arbitrary SQL functions such as 'AVG' or 'MAX'. The function (or functions) should be the return values from the functions exported by the SQLMaker subclass that you are using. Please see Using SQL Functions in the Alzabo manpage for more details.
The return value of this method is highly context sensitive.
If you only requested a single function ( DISTINCT(foo) ), then it
returns the first value in scalar context and all the values in list
context.
If you requested multiple functions ( AVG(foo), MAX(foo) ) then it
returns a single array reference (the first row of values) in scalar
context and a list of array references in list context.
The Alzabo::Runtime::Schema object to which this table
belongs.
The name of the table.
The Alzabo::Runtime::Column object that matches the name
given.
A list of Alzabo::Runtime::Column objects that match the
list of names given. If no list is provided, then it returns all
column objects for the table.
A primary key is one or more columns which must be unique in each row of the table. For a multi-column primary key, than the values of the columns taken in order must be unique. The order of a multi-column key is significant as most RDBMS's will create an index on the primary key using the same column order as is specified and column order usually matters in indexes.
An ordered list of column objects that make up the primary key for the table.
Alzabo::Runtime::Column object)This method is really only needed if you're not sure that column
belongs to the table. Otherwise just call the
Alzabo::Runtime::Column->is_primary_key
method on the column object.
A boolean value indicating whether or not the column given is part of the table's primary key.
A list of Alzabo::Runtime::ForeignKey objects from the
given column to the given table, if they exist. In scalar context,
returns the first item in the list. There is no guarantee as to what
the first item will be.
Alzabo::Runtime::Table object)
A list of all the Alzabo::Runtime::ForeignKey objects
to the given table. In scalar context, returns the first item in the
list. There is no guarantee as to what the first item will be.
Alzabo::Runtime::Column object)Returns a list of all the Alzabo::Runtime::ForeignKey
objects that the given column is a part of, if any. In scalar
context, returns the first item in the list. There is no guarantee as
to what the first item will be.
A list of all the Alzabo::Runtime::ForeignKey objects
for this table. In scalar context, returns the first item in the
list. There is no guarantee as to what the first item will be.
This method expect an index id as returned by the
Alzabo::Runtime::Index->id method.
The Alzabo::Runtime::Index object matching this id, if it
exists in the table.
All the Alzabo::Runtime::Index objects for the table.
This concept was taken directly from Michael Schwern's Class::DBI module (credit where it is due).
This lazy loading is only done when caching is turned on. Otherwise, Alzabo always fetches data from the database when it is requested and does not store it locally in memory at all. In fact, trying to use lazy column loading without caching will simply slow things down.
By default, Alzabo::Runtime::Row objects
only load data from the database as it is requested via the select
method. This is stored internally in the object after being fetched.
If the object is expired in the cache, it will erase this information
and fetch it from the database again as needed.
This is good because it saves on memory and makes object creation quicker, but it is bad because you could potentially end up with one SQL call per column (excluding primary key columns, which are usually not fetched from the database).
This class provides two method to help you handle this potential problem. Basically these methods allow you to declare usage patterns for the table.
The first method,
set_prefetch, allows you to specify a list of columns to be fetched
immediately after object creation or after an object discovers it is
expired in the cache. These should be columns that you expect to use
extremely frequently.
The second method, add_group,
allows you to group columns together. If you attempt to fetch one of
these columns, then all the columns in the group will be fetched.
This is useful in cases where you don't often want certain data, but
when you do you need several related pieces.
Alzabo::Column objects)Given a list of column objects, this makes sure that all
Alzabo::Runtime::Row objects fetch this
data as soon as they are created, as well as immediately after they
know they have been expired in the cache.
NOTE: It is pointless (though not an error) to give primary key column here as these are always prefetched (in a sense).
Alzabo::Column objects)Given a list of Alzabo::Column objects, this
method creates a group containing these columns. This means that if
any column in the group is fetched from the database, then they will
all be fetched. Otherwise column are always fetched singly.
Currently, a column cannot be part of more than one group.
NOTE: It is pointless to include a column that was given to the
set_prefetch method in a group here, as it always fetched as soon as
possible.
This method primarily exists for use by the
Alzabo::Runtime::Row class.
A list of column names (not objects) that should be prefetched.
This method primarily exists for use by the
Alzabo::Runtime::Row class.
A list of column names representing the group that this column is part of. If the column named is not part of a group, only the name passed in is returned.
Dave Rolsky, <autarch@urth.org>
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Alzabo::Runtime::Table - Table objects |