# == The +after_find+ and +after_initialize+ exceptions
#
# Because +after_find+ and +after_initialize+ are called for each object found and instantiated by a finder, such as <tt>Base.find(:all)</tt>, we've had
# to implement a simple performance constraint (50% more speed on a simple test case). Unlike all the other callbacks, +after_find+ and
# +after_initialize+ will only be run if an explicit implementation is defined (<tt>def after_find</tt>). In that case, all of the
# Because +after_find+ and +after_initialize+ are called for each object found and instantiated by a finder,
# such as <tt>Base.find(:all)</tt>, we've had to implement a simple performance constraint (50% more speed
# on a simple test case). Unlike all the other callbacks, +after_find+ and +after_initialize+ will only be
# run if an explicit implementation is defined (<tt>def after_find</tt>). In that case, all of the
# If the returning value of a +before_validation+ callback can be evaluated to +false+, the process will be aborted and <tt>Base#save</tt> will return +false+.
# If Base#save! is called it will raise a ActiveRecord::RecordInvalid exception.
# Nothing will be appended to the errors object.
# If the returning value of a +before_validation+ callback can be evaluated to +false+, the process will be
# aborted and <tt>Base#save</tt> will return +false+. If Base#save! is called it will raise a
# ActiveRecord::RecordInvalid exception. Nothing will be appended to the errors object.
#
# == Canceling callbacks
#
# If a <tt>before_*</tt> callback returns +false+, all the later callbacks and the associated action are cancelled. If an <tt>after_*</tt> callback returns
# +false+, all the later callbacks are cancelled. Callbacks are generally run in the order they are defined, with the exception of callbacks
# defined as methods on the model, which are called last.
# If a <tt>before_*</tt> callback returns +false+, all the later callbacks and the associated action are
# cancelled. If an <tt>after_*</tt> callback returns +false+, all the later callbacks are cancelled.
# Callbacks are generally run in the order they are defined, with the exception of callbacks defined as
# methods on the model, which are called last.
#
# == Transactions
#
...
...
@@ -217,7 +220,8 @@ module ActiveRecord
#
# == Debugging callbacks
#
# To list the methods and procs registered with a particular callback, append <tt>_callback_chain</tt> to the callback name that you wish to list and send that to your class from the Rails console:
# To list the methods and procs registered with a particular callback, append <tt>_callback_chain</tt> to
# the callback name that you wish to list and send that to your class from the Rails console:
# Available options are (none of these exists by default):
# * <tt>:limit</tt> -
# Requests a maximum column length. This is number of characters for <tt>:string</tt> and <tt>:text</tt> columns and number of bytes for :binary and :integer columns.
# Requests a maximum column length. This is number of characters for <tt>:string</tt> and
# <tt>:text</tt> columns and number of bytes for :binary and :integer columns.
# * <tt>:default</tt> -
# The column's default value. Use nil for NULL.
# * <tt>:null</tt> -
...
...
@@ -462,8 +464,8 @@ def [](name)
# TableDefinition#timestamps that'll add created_at and +updated_at+ as datetimes.
#
# TableDefinition#references will add an appropriately-named _id column, plus a corresponding _type
# column if the <tt>:polymorphic</tt> option is supplied. If <tt>:polymorphic</tt> is a hash of options, these will be
# used when creating the <tt>_type</tt> column. So what can be written like this:
# column if the <tt>:polymorphic</tt> option is supplied. If <tt>:polymorphic</tt> is a hash of
# options, these will be used when creating the <tt>_type</tt> column. So what can be written like this:
# * <tt>:database</tt> - The name of the database. No default, must be provided.
# * <tt>:schema_search_path</tt> - An optional schema search path for the connection given as a string of comma-separated schema names. This is backward-compatible with the <tt>:schema_order</tt> option.
# * <tt>:encoding</tt> - An optional client encoding that is used in a <tt>SET client_encoding TO <encoding></tt> call on the connection.
# * <tt>:min_messages</tt> - An optional client min messages that is used in a <tt>SET client_min_messages TO <min_messages></tt> call on the connection.
# * <tt>:allow_concurrency</tt> - If true, use async query methods so Ruby threads don't deadlock; otherwise, use blocking query methods.
# * <tt>:schema_search_path</tt> - An optional schema search path for the connection given
# as a string of comma-separated schema names. This is backward-compatible with the <tt>:schema_order</tt> option.
# * <tt>:encoding</tt> - An optional client encoding that is used in a <tt>SET client_encoding TO
# <encoding></tt> call on the connection.
# * <tt>:min_messages</tt> - An optional client min messages that is used in a
# <tt>SET client_min_messages TO <min_messages></tt> call on the connection.
# * <tt>:allow_concurrency</tt> - If true, use async query methods so Ruby threads don't deadlock;
# Count operates using three different approaches.
#
# * Count all: By not passing any parameters to count, it will return a count of all the rows for the model.
# * Count using column: By passing a column name to count, it will return a count of all the rows for the model with supplied column present
# * Count using column: By passing a column name to count, it will return a count of all the
# rows for the model with supplied column present
# * Count using options will find the row count matched by the options used.
#
# The third approach, count using options, accepts an option hash as the only parameter. The options are:
#
# * <tt>:conditions</tt>: An SQL fragment like "administrator = 1" or [ "user_name = ?", username ]. See conditions in the intro to ActiveRecord::Base.
# * <tt>:conditions</tt>: An SQL fragment like "administrator = 1" or [ "user_name = ?", username ].
# See conditions in the intro to ActiveRecord::Base.
# * <tt>:joins</tt>: Either an SQL fragment for additional joins like "LEFT JOIN comments ON comments.post_id = id" (rarely needed)
# or named associations in the same form used for the <tt>:include</tt> option, which will perform an INNER JOIN on the associated table(s).
# If the value is a string, then the records will be returned read-only since they will have attributes that do not correspond to the table's columns.
# or named associations in the same form used for the <tt>:include</tt> option, which will
# perform an INNER JOIN on the associated table(s).
# If the value is a string, then the records will be returned read-only since they will have
# attributes that do not correspond to the table's columns.
# Pass <tt>:readonly => false</tt> to override.
# * <tt>:include</tt>: Named associations that should be loaded alongside using LEFT OUTER JOINs. The symbols named refer
# to already defined associations. When using named associations, count returns the number of DISTINCT items for the model you're counting.
# * <tt>:include</tt>: Named associations that should be loaded alongside using LEFT OUTER JOINs.
# The symbols named refer to already defined associations. When using named associations, count
# returns the number of DISTINCT items for the model you're counting.
# See eager loading under Associations.
# * <tt>:order</tt>: An SQL fragment like "created_at DESC, name" (really only used with GROUP BY calculations).
# * <tt>:group</tt>: An attribute name by which the result should be grouped. Uses the GROUP BY SQL-clause.
# * <tt>:select</tt>: By default, this is * as in SELECT * FROM, but can be changed if you, for example, want to do a join but not
# * <tt>:select</tt>: By default, this is * as in SELECT * FROM, but can be changed if you, for example,
# want to do a join but not
# include the joined columns.
# * <tt>:distinct</tt>: Set this to true to make this a distinct calculation, such as SELECT COUNT(DISTINCT posts.id) ...
# * <tt>:from</tt> - By default, this is the table name of the class, but can be changed to an alternate table name (or even the name
# of a database view).
# * <tt>:distinct</tt>: Set this to true to make this a distinct calculation, such as
# SELECT COUNT(DISTINCT posts.id) ...
# * <tt>:from</tt> - By default, this is the table name of the class, but can be changed to an
# alternate table name (or even the name of a database view).
#
# Examples for counting all:
# Person.count # returns the total count of all people
...
...
@@ -34,12 +41,19 @@ module Calculations
#
# Examples for count with options:
# Person.count(:conditions => "age > 26")
# Person.count(:conditions => "age > 26 AND job.salary > 60000", :include => :job) # because of the named association, it finds the DISTINCT count using LEFT OUTER JOIN.
# Person.count(:conditions => "age > 26 AND job.salary > 60000", :joins => "LEFT JOIN jobs on jobs.person_id = person.id") # finds the number of rows matching the conditions and joins.
#
# # because of the named association, it finds the DISTINCT count using LEFT OUTER JOIN.
# This calculates aggregate values in the given column. Methods for count, sum, average, minimum, and maximum have been added as shortcuts.
# Options such as <tt>:conditions</tt>, <tt>:order</tt>, <tt>:group</tt>, <tt>:having</tt>, and <tt>:joins</tt> can be passed to customize the query.
# This calculates aggregate values in the given column. Methods for count, sum, average,
# minimum, and maximum have been added as shortcuts. Options such as <tt>:conditions</tt>,
# <tt>:order</tt>, <tt>:group</tt>, <tt>:having</tt>, and <tt>:joins</tt> can be passed to customize the query.
#
# There are two basic forms of output:
# * Single aggregate value: The single value is type cast to Fixnum for COUNT, Float for AVG, and the given column's type for everything else.
# * Grouped values: This returns an ordered hash of the values and groups them by the <tt>:group</tt> option. It takes either a column name, or the name
# of a belongs_to association.
# * Single aggregate value: The single value is type cast to Fixnum for COUNT, Float
# for AVG, and the given column's type for everything else.
# * Grouped values: This returns an ordered hash of the values and groups them by the
# <tt>:group</tt> option. It takes either a column name, or the name of a belongs_to association.
# * <tt>:conditions</tt> - An SQL fragment like "administrator = 1" or [ "user_name = ?", username ]. See conditions in the intro to ActiveRecord::Base.
# * <tt>:include</tt>: Eager loading, see Associations for details. Since calculations don't load anything, the purpose of this is to access fields on joined tables in your conditions, order, or group clauses.
# * <tt>:joins</tt> - An SQL fragment for additional joins like "LEFT JOIN comments ON comments.post_id = id". (Rarely needed).
# The records will be returned read-only since they will have attributes that do not correspond to the table's columns.
# * <tt>:conditions</tt> - An SQL fragment like "administrator = 1" or [ "user_name = ?", username ].
# See conditions in the intro to ActiveRecord::Base.
# * <tt>:include</tt>: Eager loading, see Associations for details. Since calculations don't load anything,
# the purpose of this is to access fields on joined tables in your conditions, order, or group clauses.
# * <tt>:joins</tt> - An SQL fragment for additional joins like "LEFT JOIN comments ON comments.post_id = id".
# (Rarely needed).
# The records will be returned read-only since they will have attributes that do not correspond to the
# table's columns.
# * <tt>:order</tt> - An SQL fragment like "created_at DESC, name" (really only used with GROUP BY calculations).
# * <tt>:group</tt> - An attribute name by which the result should be grouped. Uses the GROUP BY SQL-clause.
# * <tt>:select</tt> - By default, this is * as in SELECT * FROM, but can be changed if you for example want to do a join, but not
# include the joined columns.
# * <tt>:distinct</tt> - Set this to true to make this a distinct calculation, such as SELECT COUNT(DISTINCT posts.id) ...
# * <tt>:select</tt> - By default, this is * as in SELECT * FROM, but can be changed if you for example
# want to do a join, but not include the joined columns.
# * <tt>:distinct</tt> - Set this to true to make this a distinct calculation, such as
# SELECT COUNT(DISTINCT posts.id) ...
#
# Examples:
# Person.calculate(:count, :all) # The same as Person.count
# Person.average(:age) # SELECT AVG(age) FROM people...
# Person.minimum(:age, :conditions => ['last_name != ?', 'Drake']) # Selects the minimum age for everyone with a last name other than 'Drake'
# Person.minimum(:age, :having => 'min(age) > 17', :group => :last_name) # Selects the minimum age for any family without any minors
# Person.minimum(:age, :conditions => ['last_name != ?', 'Drake']) # Selects the minimum age for
# # everyone with a last name other than 'Drake'
#
# # Selects the minimum age for any family without any minors
# * <tt>:conditions</tt> - An SQL fragment like "administrator = 1", <tt>[ "user_name = ?", username ]</tt>, or <tt>["user_name = :user_name", { :user_name => user_name }]</tt>. See conditions in the intro.
# * <tt>:conditions</tt> - An SQL fragment like "administrator = 1", <tt>[ "user_name = ?", username ]</tt>,
# or <tt>["user_name = :user_name", { :user_name => user_name }]</tt>. See conditions in the intro.
# * <tt>:order</tt> - An SQL fragment like "created_at DESC, name".
# * <tt>:group</tt> - An attribute name by which the result should be grouped. Uses the <tt>GROUP BY</tt> SQL-clause.
# * <tt>:having</tt> - Combined with +:group+ this can be used to filter the records that a <tt>GROUP BY</tt> returns. Uses the <tt>HAVING</tt> SQL-clause.
# * <tt>:having</tt> - Combined with +:group+ this can be used to filter the records that a
# <tt>GROUP BY</tt> returns. Uses the <tt>HAVING</tt> SQL-clause.
# * <tt>:limit</tt> - An integer determining the limit on the number of rows that should be returned.
# * <tt>:offset</tt> - An integer determining the offset from where the rows should be fetched. So at 5, it would skip rows 0 through 4.
# * <tt>:offset</tt> - An integer determining the offset from where the rows should be fetched. So at 5,
# it would skip rows 0 through 4.
# * <tt>:joins</tt> - Either an SQL fragment for additional joins like "LEFT JOIN comments ON comments.post_id = id" (rarely needed),
# named associations in the same form used for the <tt>:include</tt> option, which will perform an <tt>INNER JOIN</tt> on the associated table(s),
# named associations in the same form used for the <tt>:include</tt> option, which will perform an
# <tt>INNER JOIN</tt> on the associated table(s),
# or an array containing a mixture of both strings and named associations.
# If the value is a string, then the records will be returned read-only since they will have attributes that do not correspond to the table's columns.
# If the value is a string, then the records will be returned read-only since they will
# have attributes that do not correspond to the table's columns.
# Pass <tt>:readonly => false</tt> to override.
# * <tt>:include</tt> - Names associations that should be loaded alongside. The symbols named refer
# to already defined associations. See eager loading under Associations.
# * <tt>:select</tt> - By default, this is "*" as in "SELECT * FROM", but can be changed if you, for example, want to do a join but not
# include the joined columns. Takes a string with the SELECT SQL fragment (e.g. "id, name").
# * <tt>:from</tt> - By default, this is the table name of the class, but can be changed to an alternate table name (or even the name
# of a database view).
# * <tt>:select</tt> - By default, this is "*" as in "SELECT * FROM", but can be changed if you,
# for example, want to do a join but not include the joined columns. Takes a string with the SELECT SQL fragment (e.g. "id, name").
# * <tt>:from</tt> - By default, this is the table name of the class, but can be changed
# to an alternate table name (or even the name of a database view).
# * <tt>:readonly</tt> - Mark the returned records read-only so they cannot be saved or updated.
# * <tt>:lock</tt> - An SQL fragment like "FOR UPDATE" or "LOCK IN SHARE MODE".
