Class: ROM::SQL::Commands::Postgres::Upsert

Inherits:
Create
  • Object
show all
Defined in:
lib/rom/sql/extensions/postgres/commands.rb

Overview

Upsert command

Uses a feature of PostgreSQL 9.5 commonly called an “upsert”. The command been called attempts to perform an insert and can make an update (or silently do nothing) in case of the insertion was unsuccessful due to a violation of a unique constraint. Very important implementation detail is that the whole operation is atomic, i.e. aware of concurrent transactions, and doesn’t raise exceptions if used properly.

See PG’s docs in INSERT statement for details www.postgresql.org/docs/current/static/sql-insert.html

Normally, the command should configured via class level settings. By default, that is without any settings provided, the command uses ON CONFLICT DO NOTHING clause.

This implementation uses Sequel’s API underneath, the docs are available at sequel.jeremyevans.net/rdoc-adapters/classes/Sequel/Postgres/DatasetMethods.html#method-i-insert_conflict

Instance Attribute Summary collapse

Instance Method Summary collapse

Instance Attribute Details

#conflict_target ⇒ Object (readonly)

Returns the column or expression to handle a violation on.

Returns:

  • (Object) —

    the column or expression to handle a violation on



76
 
# File 'lib/rom/sql/extensions/postgres/commands.rb', line 76

option :conflict_target, reader: true, default: -> c { c.class.conflict_target }

#constraint ⇒ Symbol (readonly)

Returns the name of the constraint expected to be violated.

Returns:

  • (Symbol) —

    the name of the constraint expected to be violated



72
 
# File 'lib/rom/sql/extensions/postgres/commands.rb', line 72

option :constraint, reader: true, default: -> c { c.class.constraint }

#update_statement ⇒ Object (readonly)

Returns the update statement which will be executed in case of a violation.

Returns:

  • (Object) —

    the update statement which will be executed in case of a violation



80
 
# File 'lib/rom/sql/extensions/postgres/commands.rb', line 80

option :update_statement, reader: true, default: -> c { c.class.update_statement }

#update_where ⇒ Object (readonly)

Returns the WHERE clause to be added to the update.

Returns:

  • (Object) —

    the WHERE clause to be added to the update



84
 
# File 'lib/rom/sql/extensions/postgres/commands.rb', line 84

option :update_where, reader: true, default: -> c { c.class.update_where }

Instance Method Details

#execute(tuples) ⇒ Array<Hash>

Tries to insert provided tuples and do an update (or nothing) when the inserted record violates a unique constraint and hence cannot be appended to the table

Returns:

  • (Array<Hash>) 


93
94
95
96
97
98
99
 
# File 'lib/rom/sql/extensions/postgres/commands.rb', line 93

def execute(tuples)
  inserted_tuples = with_input_tuples(tuples) do |tuple|
    upsert(input[tuple], upsert_options)
  end

  inserted_tuples.flatten(1)
end

#upsert_options ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future. 



102
103
104
105
106
107
108
109
 
# File 'lib/rom/sql/extensions/postgres/commands.rb', line 102

def upsert_options
  @upsert_options ||= {
    constraint: constraint,
    target: conflict_target,
    update_where: update_where,
    update: update_statement
  }
end