Module: Switchman::ActiveRecord::QueryMethods

Defined in:
lib/switchman/active_record/query_methods.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Instance Attribute Details

#shard_source_value ⇒ Object

shard_value is one of:

A shard
An array or relation of shards
An AR object (query runs against that object's associated_shards)

shard_source_value is one of:

:implicit - inferred from current shard when relation was created, or primary key where clause
:explicit - explicit set on the relation
:to_a - a special value that Relation#to_a uses when querying multiple shards to
        remove primary keys from conditions that aren't applicable to the current shard



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# File 'lib/switchman/active_record/query_methods.rb', line 13

def shard_source_value
  @shard_source_value
end

#shard_value ⇒ Object

shard_value is one of:

A shard
An array or relation of shards
An AR object (query runs against that object's associated_shards)

shard_source_value is one of:

:implicit - inferred from current shard when relation was created, or primary key where clause
:explicit - explicit set on the relation
:to_a - a special value that Relation#to_a uses when querying multiple shards to
        remove primary keys from conditions that aren't applicable to the current shard



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# File 'lib/switchman/active_record/query_methods.rb', line 13

def shard_value
  @shard_value
end

Instance Method Details

#build_where(opts, other = []) ⇒ Object 



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# File 'lib/switchman/active_record/query_methods.rb', line 45

def build_where(opts, other = [])
  source_shard = Shard.current(klass.shard_category)
  case opts
  when Hash, Arel::Nodes::Node
    predicates = super
    infer_shards_from_primary_key(predicates) if shard_source_value == :implicit && shard_value.is_a?(Shard)
    predicates = transpose_predicates(predicates, source_shard, primary_shard) if shard_source_value != :explicit
    predicates
  else
    super
  end
end

#having(opts, *rest) ⇒ Object 



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# File 'lib/switchman/active_record/query_methods.rb', line 37

def having(opts, *rest)
  return self if opts.blank?

  relation = clone
  relation.having_values += relation.build_where(opts, rest)
  relation
end

#primary_shard ⇒ Object

the shard that where_values are relative to. if it’s multiple shards, they’re stored relative to the first shard



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# File 'lib/switchman/active_record/query_methods.rb', line 60

def primary_shard
  case shard_value
  when Shard, DefaultShard
    shard_value
  # associated_shards
  when ::ActiveRecord::Base
    shard_value.shard
  when Array
    shard_value.first
  when ::ActiveRecord::Relation
    Shard.default
  else
    raise ArgumentError("invalid shard value #{shard_value}")
  end
end

#shard(value, source = :explicit) ⇒ Object 



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# File 'lib/switchman/active_record/query_methods.rb', line 15

def shard(value, source = :explicit)
  relation = clone
  relation.shard_value = value
  relation.shard_source_value = source
  if (primary_shard != relation.primary_shard || source == :to_a)
    relation.where_values = relation.transpose_predicates(relation.where_values, primary_shard, relation.primary_shard, source == :to_a) if !relation.where_values.empty?
    relation.having_values = relation.transpose_predicates(relation.having_values, primary_shard, relation.primary_shard, source == :to_a) if !relation.having_values.empty?
  end
  relation
end

#transpose_predicates(predicates, source_shard, target_shard, remove_nonlocal_primary_keys = false) ⇒ Object 



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# File 'lib/switchman/active_record/query_methods.rb', line 146

def transpose_predicates(predicates, source_shard, target_shard, remove_nonlocal_primary_keys = false)
  predicates.map do |predicate|
    next predicate unless predicate.is_a?(Arel::Nodes::Binary) && type = transposable_attribute_type(predicate.left)

    remove = true if type == :primary && remove_nonlocal_primary_keys && predicate.left.relation.engine == klass

    new_right_value = case predicate.right
    when Array
      local_ids = []
      predicate.right.each do |value|
        local_id = Shard.relative_id_for(value, source_shard, target_shard)
        local_ids << local_id unless remove && local_id > Shard::IDS_PER_SHARD
      end
      local_ids
    when Arel::Nodes::BindParam
      # look for a bind param with a matching column name
      if @bind_params && idx = @bind_params.find_index{|b| b.is_a?(Array) && b.first.try(:name) == predicate.left}
        column, value = @bind_params[idx]
        local_id = Shard.relative_id_for(value, source_shard, target_shard)
        local_id = [] if remove && local_id > Shard::IDS_PER_SHARD
        @bind_params[idx] = [column, local_id]
      end
      predicate.right
    else
      local_id = Shard.relative_id_for(predicate.right, source_shard, target_shard)
      local_id = [] if remove && local_id > Shard::IDS_PER_SHARD
      local_id
    end

    if new_right_value == predicate.right
      predicate
    else
      predicate.class.new(predicate.left, new_right_value)
    end
  end
end

#where(opts, *rest) ⇒ Object

replace these with versions that call build_where on the result relation, not the source relation (so build_where is able to implicitly change the shard_value)



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# File 'lib/switchman/active_record/query_methods.rb', line 29

def where(opts, *rest)
  return self if opts.blank?

  relation = clone
  relation.where_values += relation.build_where(opts, rest)
  relation
end