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Merge remote branch 'docrails/master'
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commit
8b2e4fddbf
4 changed files with 54 additions and 59 deletions
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@ -269,8 +269,9 @@ module ActionView
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# The +options+ hash accepts the same options as url_for.
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#
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# There are a few special +html_options+:
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# * <tt>:method</tt> - Specifies the anchor name to be appended to the path.
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# * <tt>:disabled</tt> - Specifies the anchor name to be appended to the path.
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# * <tt>:method</tt> - Symbol of HTTP verb. Supported verbs are <tt>:post</tt>, <tt>:get</tt>,
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# <tt>:delete</tt> and <tt>:put</tt>. By default it will be <tt>:post</tt>.
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# * <tt>:disabled</tt> - If set to true, it will generate a disabled button.
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# * <tt>:confirm</tt> - This will use the unobtrusive JavaScript driver to
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# prompt with the question specified. If the user accepts, the link is
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# processed normally, otherwise no action is taken.
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@ -234,7 +234,7 @@ h4. Array Conditions
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Now what if that number could vary, say as an argument from somewhere, or perhaps from the user's level status somewhere? The find then becomes something like:
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<ruby>
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Client.where(["orders_count = ?", params[:orders]])
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Client.where("orders_count = ?", params[:orders])
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</ruby>
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Active Record will go through the first element in the conditions value and any additional elements will replace the question marks +(?)+ in the first element.
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@ -242,7 +242,7 @@ Active Record will go through the first element in the conditions value and any
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Or if you want to specify two conditions, you can do it like:
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<ruby>
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Client.where(["orders_count = ? AND locked = ?", params[:orders], false])
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Client.where("orders_count = ? AND locked = ?", params[:orders], false)
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</ruby>
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In this example, the first question mark will be replaced with the value in +params[:orders]+ and the second will be replaced with the SQL representation of +false+, which depends on the adapter.
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@ -250,7 +250,7 @@ In this example, the first question mark will be replaced with the value in +par
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The reason for doing code like:
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<ruby>
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Client.where(["orders_count = ?", params[:orders]])
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Client.where("orders_count = ?", params[:orders])
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</ruby>
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instead of:
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@ -268,8 +268,8 @@ h5. Placeholder Conditions
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Similar to the +(?)+ replacement style of params, you can also specify keys/values hash in your array conditions:
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<ruby>
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Client.where(
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["created_at >= :start_date AND created_at <= :end_date", { :start_date => params[:start_date], :end_date => params[:end_date] }])
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Client.where("created_at >= :start_date AND created_at <= :end_date",
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{:start_date => params[:start_date], :end_date => params[:end_date]})
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</ruby>
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This makes for clearer readability if you have a large number of variable conditions.
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@ -279,8 +279,8 @@ h5(#array-range_conditions). Range Conditions
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If you're looking for a range inside of a table (for example, users created in a certain timeframe) you can use the conditions option coupled with the +IN+ SQL statement for this. If you had two dates coming in from a controller you could do something like this to look for a range:
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<ruby>
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Client.where(["created_at IN (?)",
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(params[:start_date].to_date)..(params[:end_date].to_date)])
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Client.where("created_at IN (?)",
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(params[:start_date].to_date)..(params[:end_date].to_date))
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</ruby>
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This would generate the proper query which is great for small ranges but not so good for larger ranges. For example if you pass in a range of date objects spanning a year that's 365 (or possibly 366, depending on the year) strings it will attempt to match your field against.
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@ -301,8 +301,8 @@ h5. Time and Date Conditions
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Things can get *really* messy if you pass in Time objects as it will attempt to compare your field to *every second* in that range:
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<ruby>
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Client.where(["created_at IN (?)",
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(params[:start_date].to_date.to_time)..(params[:end_date].to_date.to_time)])
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Client.where("created_at IN (?)",
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(params[:start_date].to_date.to_time)..(params[:end_date].to_date.to_time))
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</ruby>
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<sql>
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@ -323,14 +323,14 @@ In this example it would be better to use greater-than and less-than operators i
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<ruby>
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Client.where(
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["created_at > ? AND created_at < ?", params[:start_date], params[:end_date]])
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"created_at > ? AND created_at < ?", params[:start_date], params[:end_date])
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</ruby>
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You can also use the greater-than-or-equal-to and less-than-or-equal-to like this:
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<ruby>
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Client.where(
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["created_at >= ? AND created_at <= ?", params[:start_date], params[:end_date]])
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"created_at >= ? AND created_at <= ?", params[:start_date], params[:end_date])
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</ruby>
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Just like in Ruby. If you want a shorter syntax be sure to check out the "Hash Conditions":#hash-conditions section later on in the guide.
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@ -344,13 +344,13 @@ NOTE: Only equality, range and subset checking are possible with Hash conditions
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h5. Equality Conditions
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<ruby>
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Client.where({ :locked => true })
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Client.where(:locked => true)
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</ruby>
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The field name can also be a string:
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<ruby>
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Client.where({ 'locked' => true })
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Client.where('locked' => true)
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</ruby>
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h5(#hash-range_conditions). Range Conditions
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@ -358,7 +358,7 @@ h5(#hash-range_conditions). Range Conditions
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The good thing about this is that we can pass in a range for our fields without it generating a large query as shown in the preamble of this section.
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<ruby>
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Client.where({ :created_at => (Time.now.midnight - 1.day)..Time.now.midnight})
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Client.where(:created_at => (Time.now.midnight - 1.day)..Time.now.midnight)
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</ruby>
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This will find all clients created yesterday by using a +BETWEEN+ SQL statement:
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@ -374,7 +374,7 @@ h5. Subset Conditions
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If you want to find records using the +IN+ expression you can pass an array to the conditions hash:
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<ruby>
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Client.where({ :orders_count => [1,3,5] })
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Client.where(:orders_count => [1,3,5])
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</ruby>
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This code will generate SQL like this:
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@ -496,7 +496,7 @@ SQL uses the +HAVING+ clause to specify conditions on the +GROUP BY+ fields. You
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For example:
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<ruby>
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Order.group("date(created_at)".having(["created_at > ?", 1.month.ago])
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Order.group("date(created_at)".having("created_at > ?", 1.month.ago)
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</ruby>
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The SQL that would be executed would be something like this:
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@ -509,22 +509,16 @@ This will return single order objects for each day, but only for the last month.
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h4. Readonly Objects
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To explicitly disallow modification/destruction of the matching records returned in a Relation object, you could chain the +readonly+ method as +true+ to the find call.
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Any attempt to alter or destroy the readonly records will not succeed, raising an +ActiveRecord::ReadOnlyRecord+ exception. To set this option, specify it like this:
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Active Record provides +readonly+ method on a relation to explicitly disallow modification or deletion of any of the returned object. Any attempt to alter or destroy a readonly record will not succeed, raising an +ActiveRecord::ReadOnlyRecord+ exception.
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<ruby>
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Client.first.readonly(true)
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</ruby>
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For example, calling the following code will raise an +ActiveRecord::ReadOnlyRecord+ exception:
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<ruby>
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client = Client.first.readonly(true)
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client.locked = false
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client = Client.readonly.first
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client.visits += 1
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client.save
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</ruby>
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As +client+ is explicitly set to be a readonly object, the above code will raise an +ActiveRecord::ReadOnlyRecord+ exception when calling +client.save+ with an updated value of _visists_.
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h4. Locking Records for Update
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Locking is helpful for preventing race conditions when updating records in the database and ensuring atomic updates.
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@ -571,13 +565,13 @@ end
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h5. Pessimistic Locking
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Pessimistic locking uses a locking mechanism provided by the underlying database. Passing +:lock => true+ to +Model.find+ obtains an exclusive lock on the selected rows. +Model.find+ using +:lock+ are usually wrapped inside a transaction for preventing deadlock conditions.
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Pessimistic locking uses a locking mechanism provided by the underlying database. Using +lock+ when building a relation obtains an exclusive lock on the selected rows. Relations using +lock+ are usually wrapped inside a transaction for preventing deadlock conditions.
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For example:
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<ruby>
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Item.transaction do
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i = Item.first(:lock => true)
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i = Item.lock.first
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i.name = 'Jones'
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i.save
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end
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@ -592,25 +586,25 @@ Item Update (0.4ms) UPDATE `items` SET `updated_at` = '2009-02-07 18:05:56', `
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SQL (0.8ms) COMMIT
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</sql>
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You can also pass raw SQL to the +:lock+ option to allow different types of locks. For example, MySQL has an expression called +LOCK IN SHARE MODE+ where you can lock a record but still allow other queries to read it. To specify this expression just pass it in as the lock option:
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You can also pass raw SQL to the +lock+ method for allowing different types of locks. For example, MySQL has an expression called +LOCK IN SHARE MODE+ where you can lock a record but still allow other queries to read it. To specify this expression just pass it in as the lock option:
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<ruby>
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Item.transaction do
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i = Item.find(1, :lock => "LOCK IN SHARE MODE")
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i = Item.lock("LOCK IN SHARE MODE").find(1)
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i.increment!(:views)
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end
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</ruby>
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h3. Joining Tables
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<tt>Model.find</tt> provides a +:joins+ option for specifying +JOIN+ clauses on the resulting SQL. There are multiple ways to specify the +:joins+ option:
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Active Record provides a finder method called +joins+ for specifying +JOIN+ clauses on the resulting SQL. There are multiple ways to use the +joins+ method.
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h4. Using a String SQL Fragment
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You can just supply the raw SQL specifying the +JOIN+ clause to the +:joins+ option. For example:
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You can just supply the raw SQL specifying the +JOIN+ clause to +joins+:
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<ruby>
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Client.all(:joins => 'LEFT OUTER JOIN addresses ON addresses.client_id = clients.id')
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Client.joins('LEFT OUTER JOIN addresses ON addresses.client_id = clients.id')
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</ruby>
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This will result in the following SQL:
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@ -625,7 +619,7 @@ WARNING: This method only works with +INNER JOIN+,
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<br />
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Active Record lets you use the names of the "associations":association_basics.html defined on the model as a shortcut for specifying the +:joins+ option.
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Active Record lets you use the names of the "associations":association_basics.html defined on the model as a shortcut for specifying +JOIN+ clause for those associations when using the +joins+ method.
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For example, consider the following +Category+, +Post+, +Comments+ and +Guest+ models:
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@ -838,13 +832,13 @@ Client.exists?(1,2,3)
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Client.exists?([1,2,3])
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</ruby>
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The +exists+ method may also take a +conditions+ option much like find:
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It's even possible to use +exists?+ without any arguments on a model or a relation.
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<ruby>
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Client.exists?(:conditions => "first_name = 'Ryan'")
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Client.where(:first_name => 'Ryan').exists?
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</ruby>
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It's even possible to use +exists?+ without any arguments:
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The above returns +true+ if there is at least one client with the +first_name+ 'Ryan' and +false+ otherwise.
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<ruby>
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Client.exists?
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@ -856,22 +850,24 @@ h3. Calculations
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This section uses count as an example method in this preamble, but the options described apply to all sub-sections.
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<tt>count</tt> takes conditions much in the same way +exists?+ does:
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All calculation methods work directly on a model:
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<ruby>
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Client.count(:conditions => "first_name = 'Ryan'")
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Client.count
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# SELECT count(*) AS count_all FROM clients
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</ruby>
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Which will execute:
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<sql>
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SELECT count(*) AS count_all FROM clients WHERE (first_name = 'Ryan')
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</sql>
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You can also use the +includes+ or +joins+ methods for this to do something a little more complex:
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Or on a relation :
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<ruby>
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Client.where("clients.first_name = 'Ryan' AND orders.status = 'received'").includes("orders").count
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Client.where(:first_name => 'Ryan').count
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# SELECT count(*) AS count_all FROM clients WHERE (first_name = 'Ryan')
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</ruby>
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You can also use various finder methods on a relation for performing complex calculations:
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<ruby>
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Client.includes("orders").where(:first_name => 'Ryan', :orders => {:status => 'received'}).count
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</ruby>
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Which will execute:
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@ -882,8 +878,6 @@ SELECT count(DISTINCT clients.id) AS count_all FROM clients
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(clients.first_name = 'Ryan' AND orders.status = 'received')
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</sql>
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This code specifies +clients.first_name+ just in case one of the join tables has a field also called +first_name+ and it uses +orders.status+ because that's the name of our join table.
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h4. Count
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If you want to see how many records are in your model's table you could call +Client.count+ and that will return the number. If you want to be more specific and find all the clients with their age present in the database you can use +Client.count(:age)+.
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@ -1087,7 +1087,7 @@ Partials are very useful in rendering collections. When you pass a collection to
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When a partial is called with a pluralized collection, then the individual instances of the partial have access to the member of the collection being rendered via a variable named after the partial. In this case, the partial is +_product+, and within the +_product+ partial, you can refer to +product+ to get the instance that is being rendered.
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In Rails 3.0 there is also a shorthand for this, assuming +@posts+ is a collection of +post+ instances, you can simply do in the +index.html.erb+:
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In Rails 3.0 there is also a shorthand for this, assuming +@products+ is a collection of +product+ instances, you can simply do in the +index.html.erb+:
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<erb>
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<h1>Products</h1>
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@ -20,7 +20,7 @@ In a freshly generated Rails application, +test/performance/browsing_test.rb+ co
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<ruby>
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require 'test_helper'
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require 'performance_test_help'
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require 'rails/performance_test_help'
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# Profiling results for each test method are written to tmp/performance.
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class BrowsingTest < ActionController::PerformanceTest
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@ -34,17 +34,17 @@ This example is a simple performance test case for profiling a GET request to th
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h4. Generating Performance Tests
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Rails provides a generator called +performance_test+ for creating new performance tests:
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Rails provides a generator called +test_unit:performance+ for creating new performance tests:
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<shell>
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rails generate performance_test homepage
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rails generate test_unit:performance homepage
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</shell>
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This generates +homepage_test.rb+ in the +test/performance+ directory:
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<ruby>
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require 'test_helper'
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require 'performance_test_help'
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require 'rails/performance_test_help'
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class HomepageTest < ActionController::PerformanceTest
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# Replace this with your real tests.
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@ -103,7 +103,7 @@ Here's the performance test for +HomeController#dashboard+ and +PostsController#
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<ruby>
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require 'test_helper'
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require 'performance_test_help'
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require 'rails/performance_test_help'
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class PostPerformanceTest < ActionController::PerformanceTest
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def setup
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@ -131,7 +131,7 @@ Performance test for +Post+ model:
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<ruby>
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require 'test_helper'
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require 'performance_test_help'
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require 'rails/performance_test_help'
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class PostModelTest < ActionController::PerformanceTest
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def test_creation
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Reference in a new issue