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Class: Arel::Visitors::MySQL

Do not use. This class is for internal use only.
Relationships & Source Files
Super Chains via Extension / Inclusion / Inheritance
Class Chain:
self, ToSql, Visitor
Instance Chain:
self, ToSql, Visitor
Inherits: Arel::Visitors::ToSql
Defined in: activerecord/lib/arel/visitors/mysql.rb

Constant Summary

ToSql - Inherited

BIND_BLOCK

Class Method Summary

ToSql - Inherited

.new

Visitor - Inherited

.new, .build_dispatch_cache, .dispatch_cache

Instance Attribute Summary

Visitor - Inherited

#dispatch

Instance Method Summary

ToSql - Inherited

#compile, #aggregate, #bind_block,
#build_subselect

FIXME: we should probably have a 2-pass visitor for this.
#collect_ctes, #collect_nodes_for, #collect_optimizer_hints,
#grouping_parentheses

Used by some visitors to enclose select queries in parentheses.
#has_group_by_and_having?, #has_join_sources?, #has_limit_or_offset_or_orders?, #infix_value, #infix_value_with_paren, #inject_join, #is_distinct_from, #maybe_visit,
#prepare_delete_statement

Alias for ToSql#prepare_update_statement.
#prepare_update_statement

The default strategy for an UPDATE with joins is to use a subquery.
#prepare_update_statement_with_self_join

Used by dialects that support UPDATE ...
#quote, #quote_column_name, #quote_table_name, #require_parentheses?, #sanitize_as_sql_comment, #unboundable?, #unsupported, #visit_ActiveModel_Attribute, #visit_ActiveRecord_PredicateBuilder_ComparisonAttribute, #visit_ActiveRecord_PredicateBuilder_ComparisonValue,
#visit_ActiveSupport_Multibyte_Chars

Alias for ToSql#unsupported.
#visit_ActiveSupport_StringInquirer

Alias for ToSql#unsupported.
#visit_Arel_Attributes_Attribute, #visit_Arel_Nodes_And, #visit_Arel_Nodes_As, #visit_Arel_Nodes_Ascending, #visit_Arel_Nodes_Assignment, #visit_Arel_Nodes_Avg, #visit_Arel_Nodes_Between, #visit_Arel_Nodes_Bin, #visit_Arel_Nodes_BindParam, #visit_Arel_Nodes_BoundSqlLiteral, #visit_Arel_Nodes_Case, #visit_Arel_Nodes_CaseInsensitiveEquality, #visit_Arel_Nodes_CaseSensitiveEquality, #visit_Arel_Nodes_Casted, #visit_Arel_Nodes_Comment, #visit_Arel_Nodes_Count, #visit_Arel_Nodes_Cte, #visit_Arel_Nodes_CurrentRow, #visit_Arel_Nodes_DeleteStatement, #visit_Arel_Nodes_Descending, #visit_Arel_Nodes_Distinct, #visit_Arel_Nodes_DistinctOn, #visit_Arel_Nodes_DoesNotMatch, #visit_Arel_Nodes_Else, #visit_Arel_Nodes_Equality, #visit_Arel_Nodes_Except, #visit_Arel_Nodes_Exists, #visit_Arel_Nodes_Extract, #visit_Arel_Nodes_False, #visit_Arel_Nodes_Filter, #visit_Arel_Nodes_Following, #visit_Arel_Nodes_Fragments, #visit_Arel_Nodes_FullOuterJoin, #visit_Arel_Nodes_GreaterThan, #visit_Arel_Nodes_GreaterThanOrEqual, #visit_Arel_Nodes_Group, #visit_Arel_Nodes_Grouping, #visit_Arel_Nodes_HomogeneousIn, #visit_Arel_Nodes_In, #visit_Arel_Nodes_InfixOperation, #visit_Arel_Nodes_InnerJoin, #visit_Arel_Nodes_InsertStatement, #visit_Arel_Nodes_Intersect, #visit_Arel_Nodes_IsDistinctFrom, #visit_Arel_Nodes_IsNotDistinctFrom, #visit_Arel_Nodes_JoinSource, #visit_Arel_Nodes_LessThan, #visit_Arel_Nodes_LessThanOrEqual, #visit_Arel_Nodes_Limit, #visit_Arel_Nodes_Lock, #visit_Arel_Nodes_Matches, #visit_Arel_Nodes_Max, #visit_Arel_Nodes_Min, #visit_Arel_Nodes_NamedFunction, #visit_Arel_Nodes_NamedWindow, #visit_Arel_Nodes_Not, #visit_Arel_Nodes_NotEqual, #visit_Arel_Nodes_NotIn, #visit_Arel_Nodes_NotRegexp,
#visit_Arel_Nodes_NullsFirst

NullsFirst is available on all but MySQL, where it is redefined.
#visit_Arel_Nodes_NullsLast, #visit_Arel_Nodes_Offset, #visit_Arel_Nodes_On, #visit_Arel_Nodes_OptimizerHints, #visit_Arel_Nodes_Or, #visit_Arel_Nodes_OuterJoin, #visit_Arel_Nodes_Over, #visit_Arel_Nodes_Preceding,
#visit_Arel_Nodes_Quoted

Alias for ToSql#visit_Arel_Nodes_Casted.
#visit_Arel_Nodes_Range, #visit_Arel_Nodes_Regexp, #visit_Arel_Nodes_RightOuterJoin, #visit_Arel_Nodes_Rows, #visit_Arel_Nodes_SelectCore,
#visit_Arel_Nodes_SelectOptions

The Oracle enhanced adapter uses this private method, see https://github.com/rsim/oracle-enhanced/issues/2186.
#visit_Arel_Nodes_SelectStatement, #visit_Arel_Nodes_SqlLiteral, #visit_Arel_Nodes_StringJoin, #visit_Arel_Nodes_Sum, #visit_Arel_Nodes_TableAlias, #visit_Arel_Nodes_True, #visit_Arel_Nodes_UnaryOperation, #visit_Arel_Nodes_Union, #visit_Arel_Nodes_UnionAll, #visit_Arel_Nodes_UnqualifiedColumn, #visit_Arel_Nodes_UpdateStatement, #visit_Arel_Nodes_ValuesList, #visit_Arel_Nodes_When, #visit_Arel_Nodes_Window, #visit_Arel_Nodes_With, #visit_Arel_Nodes_WithRecursive, #visit_Arel_SelectManager, #visit_Arel_Table, #visit_Array,
#visit_BigDecimal

Alias for ToSql#unsupported.
#visit_Class

Alias for ToSql#unsupported.
#visit_Date

Alias for ToSql#unsupported.
#visit_DateTime

Alias for ToSql#unsupported.
#visit_FalseClass

Alias for ToSql#unsupported.
#visit_Float

Alias for ToSql#unsupported.
#visit_Hash

Alias for ToSql#unsupported.
#visit_Integer,
#visit_NilClass

Alias for ToSql#unsupported.
#visit_Set

Alias for ToSql#visit_Array.
#visit_String

Alias for ToSql#unsupported.
#visit_Symbol

Alias for ToSql#unsupported.
#visit_Time

Alias for ToSql#unsupported.
#visit_TrueClass

Alias for ToSql#unsupported.

Visitor - Inherited

#accept, #get_dispatch_cache, #visit

Constructor Details

This class inherits a constructor from Arel::Visitors::ToSql

Instance Method Details

#build_subselect(key, o) (private)

MySQL doesn't automatically create a temporary table for use subquery, so we have to give it some prompting in the form of a subsubquery.

[ GitHub ] 

  


# File 'activerecord/lib/arel/visitors/mysql.rb', line 97



def build_subselect(key, o)
  subselect = super

  # Materialize subquery by adding distinct
  # to work with MySQL 5.7.6 which sets optimizer_switch='derived_merge=on'
  unless has_limit_or_offset_or_orders?(subselect)
    core = subselect.cores.last
    core.set_quantifier = Arel::SelectManager::DISTINCT
  end

  Nodes::SelectStatement.new.tap do |stmt|
    core = stmt.cores.last
    core.froms = Nodes::Grouping.new(subselect).as("__active_record_temp")
    core.projections = [Arel.sql(quote_column_name(key.name), retryable: true)]
  end
end


  








  

    #prepare_delete_statement(o)   (private)
  



  

    
Alias for #prepare_update_statement.

  



  [ GitHub ]


  

  


# File 'activerecord/lib/arel/visitors/mysql.rb', line 93



alias :prepare_delete_statement :prepare_update_statement


  








  

    #prepare_update_statement(o)   (private)
    Also known as: #prepare_delete_statement
  



  

    
In the simple case, MySQL allows us to place JOINs directly into the UPDATE
query. However, this does not allow for LIMIT, OFFSET and ORDER. To support
these, we must use a subquery.

  



  [ GitHub ]


  

  


# File 'activerecord/lib/arel/visitors/mysql.rb', line 85



def prepare_update_statement(o)
  if o.offset || has_group_by_and_having?(o) ||
    has_join_sources?(o) && has_limit_or_offset_or_orders?(o)
    super
  else
    o
  end
end


  








  

    #visit_Arel_Nodes_Bin(o, collector)   (private)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/arel/visitors/mysql.rb', line 11



def visit_Arel_Nodes_Bin(o, collector)
  collector << "CAST("
  visit o.expr, collector
  collector << " AS BINARY)"
end


  








  

    #visit_Arel_Nodes_Concat(o, collector)   (private)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/arel/visitors/mysql.rb', line 38



def visit_Arel_Nodes_Concat(o, collector)
  collector << " CONCAT("
  visit o.left, collector
  collector << ", "
  visit o.right, collector
  collector << ") "
  collector
end


  








  

    #visit_Arel_Nodes_Cte(o, collector)   (private)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/arel/visitors/mysql.rb', line 76



def visit_Arel_Nodes_Cte(o, collector)
  collector << quote_table_name(o.name)
  collector << " AS "
  visit o.relation, collector
end


  








  

    #visit_Arel_Nodes_IsDistinctFrom(o, collector)   (private)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/arel/visitors/mysql.rb', line 53



def visit_Arel_Nodes_IsDistinctFrom(o, collector)
  collector << "NOT "
  visit_Arel_Nodes_IsNotDistinctFrom o, collector
end


  








  

    #visit_Arel_Nodes_IsNotDistinctFrom(o, collector)   (private)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/arel/visitors/mysql.rb', line 47



def visit_Arel_Nodes_IsNotDistinctFrom(o, collector)
  collector = visit o.left, collector
  collector << " <=> "
  visit o.right, collector
end


  








  

    #visit_Arel_Nodes_NotRegexp(o, collector)   (private)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/arel/visitors/mysql.rb', line 62



def visit_Arel_Nodes_NotRegexp(o, collector)
  infix_value o, collector, " NOT REGEXP "
end


  








  

    #visit_Arel_Nodes_NullsFirst(o, collector)   (private)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/arel/visitors/mysql.rb', line 66



def visit_Arel_Nodes_NullsFirst(o, collector)
  visit(o.expr.expr, collector) << " IS NOT NULL, "
  visit(o.expr, collector)
end


  








  

    #visit_Arel_Nodes_NullsLast(o, collector)   (private)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/arel/visitors/mysql.rb', line 71



def visit_Arel_Nodes_NullsLast(o, collector)
  visit(o.expr.expr, collector) << " IS NULL, "
  visit(o.expr, collector)
end


  








  

    #visit_Arel_Nodes_Regexp(o, collector)   (private)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/arel/visitors/mysql.rb', line 58



def visit_Arel_Nodes_Regexp(o, collector)
  infix_value o, collector, " REGEXP "
end


  








  

    #visit_Arel_Nodes_SelectCore(o, collector)   (private)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/arel/visitors/mysql.rb', line 33



def visit_Arel_Nodes_SelectCore(o, collector)
  o.froms ||= DUAL
  super
end


  








  

    #visit_Arel_Nodes_SelectStatement(o, collector)   (private)
  



  

    
:'(
To retrieve all rows from a certain offset up to the end of the result set,
you can use some large number for the second parameter.
https://dev.mysql.com/doc/refman/en/select.html

  



  [ GitHub ]


  

  


# File 'activerecord/lib/arel/visitors/mysql.rb', line 26



def visit_Arel_Nodes_SelectStatement(o, collector)
  if o.offset && !o.limit
    o.limit = Arel::Nodes::Limit.new(18446744073709551615)
  end
  super
end


  








  

    #visit_Arel_Nodes_UnqualifiedColumn(o, collector)   (private)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/arel/visitors/mysql.rb', line 17



def visit_Arel_Nodes_UnqualifiedColumn(o, collector)
  visit o.expr, collector
end