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

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

Overview

Upsert command

The command being called attempts to insert a record and if the inserted row would violate a unique constraint updates the conflicting row (or silently does nothing). A very important implementation detail is that the whole operation is serializable, i.e. aware of concurrent transactions, and doesn't raise exceptions and doesn't issue missing updates once used properly.

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

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

This implementation uses Sequel's API underneath, the docs are available at http://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_targetObject (readonly)

Returns the column or expression to handle a violation on.

Returns:

  • (Object)

    the column or expression to handle a violation on


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# File 'lib/rom/sql/extensions/postgres/commands.rb', line 96

option :conflict_target, default: -> { self.class.conflict_target }

#conflict_whereObject (readonly)

Returns the index filter, when using a partial index to determine uniqueness.

Returns:

  • (Object)

    the index filter, when using a partial index to determine uniqueness


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# File 'lib/rom/sql/extensions/postgres/commands.rb', line 100

option :conflict_where, default: -> { self.class.conflict_where }

#constraintSymbol (readonly)

Returns the name of the constraint expected to be violated.

Returns:

  • (Symbol)

    the name of the constraint expected to be violated


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# File 'lib/rom/sql/extensions/postgres/commands.rb', line 92

option :constraint, default: -> { self.class.constraint }

#update_statementObject (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


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# File 'lib/rom/sql/extensions/postgres/commands.rb', line 104

option :update_statement, default: -> { self.class.update_statement }

#update_whereObject (readonly)

Returns the WHERE clause to be added to the update.

Returns:

  • (Object)

    the WHERE clause to be added to the update


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# File 'lib/rom/sql/extensions/postgres/commands.rb', line 108

option :update_where, default: -> { self.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>)

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# File 'lib/rom/sql/extensions/postgres/commands.rb', line 117

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

  inserted_tuples.flatten(1)
end

#upsert_optionsObject

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.


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# File 'lib/rom/sql/extensions/postgres/commands.rb', line 126

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