Class: Gitlab::Database::Aggregation::ActiveRecord::Column

Inherits:
PartDefinition
  • Object
show all
Defined in:
lib/gitlab/database/aggregation/active_record/column.rb

Overview

Represents a SELECT-able column or SQL expression

  • name: name of the column or a name for the expression

  • type: defines the data type of the returned column values. Most cases this matches with the

database column’s type

  • expression (optional): Arel node for defining more complex SQL expressions

  • scope_proc (optional): hook for modifying the underlying ActiveRecord scope, for

example joining one extra table.

  • formatter (optional): how to format the data, the formatter is invoked before the

values are casted to the defined type.

  • description (optional): user friendly description of the column

Example: simple column selection

> c = Gitlab::Database::Aggregation::ActiveRecord::Column.new(:id, Integer) > scope = Issue.where(project_id: 1) > scope.select(c.to_arel({ scope: scope })).to_sql # SELECT “issues”.“id” FROM “issues” WHERE “issues”.“project_id” = 1

Example: custom SQL expression > expression = -> { Arel.sql(“(‘id_’ || id + 10)”) } # string: id_20 > c = Gitlab::Database::Aggregation::ActiveRecord::Column.new(:id_plus_ten_prefixed, String, > expression: expression) > scope = Issue.where(project_id: 1) > scope.select(c.to_arel({ scope: scope })).to_sql # SELECT (‘id_’ || id + 10) FROM “issues” WHERE “issues”.“project_id” = 1

Example: use a column from a JOIN-ed table > e = -> { Issue::Metrics.arel_table } > s = -> (scope, _ctx) { scope.joins(:metrics) } > c = Gitlab::Database::Aggregation::ActiveRecord::Column.new(:first_added_to_board_at, String,

expression: e, scope_proc: s)

> scope = Issue.where(project_id: 1) > scope = c.apply_scope(scope, nil) # This will be invoked by the aggregation engine > scope.select(c.to_arel({ scope: scope })).to_sql # SELECT “issue_metrics”.“first_added_to_board_at” FROM “issues” # INNER JOIN “issue_metrics” ON “issue_metrics”.“issue_id” = “issues”.“id” # WHERE “issues”.“project_id” = 1

Direct Known Subclasses

Count, DateBucketDimension, Mean

Instance Attribute Summary

Attributes inherited from PartDefinition

#description, #expression, #formatter, #name, #secondary_expression, #type

Instance Method Summary collapse

Methods inherited from PartDefinition

#format_value, #identifier, #initialize, #instance_key, #parameterized?, #validate_part

Constructor Details

This class inherits a constructor from Gitlab::Database::Aggregation::PartDefinition

Instance Method Details

#to_arel(context) ⇒ Object

Returns an Arel node representing this column or metric in a SELECT statement. Subclasses may wrap the expression (e.g., date_trunc, AVG, COUNT).



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# File 'lib/gitlab/database/aggregation/active_record/column.rb', line 47

def to_arel(context)
  expression ? expression.call : context[:scope].arel_table[name]
end