Class: PG::BasicTypeMapBasedOnResult

Inherits:

TypeMapByOid

• Object
• TypeMap
• TypeMapByOid
• PG::BasicTypeMapBasedOnResult

Includes:

BasicTypeRegistry

Defined in:

lib/pg/basic_type_mapping.rb

Overview

Simple set of rules for type casting common PostgreSQL types from Ruby to PostgreSQL.

OIDs of supported type casts are not hard-coded in the sources, but are retrieved from the PostgreSQL’s pg_type table in PG::BasicTypeMapBasedOnResult.new .

This class works equal to PG::BasicTypeMapForResults, but does not define decoders for the given result OIDs, but encoders. So it can be used to type cast field values based on the type OID retrieved by a separate SQL query.

PG::TypeMapByOid#build_column_map(result) can be used to generate a result independent PG::TypeMapByColumn type map, which can subsequently be used to cast query bind parameters or #put_copy_data fields.

Example:

conn.exec( "CREATE TEMP TABLE copytable (t TEXT, i INT, ai INT[])" )

# Retrieve table OIDs per empty result set.
res = conn.exec( "SELECT * FROM copytable LIMIT 0" )
# Build a type map for common ruby to database type encoders.
btm = PG::BasicTypeMapBasedOnResult.new(conn)
# Build a PG::TypeMapByColumn with encoders suitable for copytable.
tm = btm.build_column_map( res )
row_encoder = PG::TextEncoder::CopyRow.new type_map: tm

conn.copy_data( "COPY copytable FROM STDIN", row_encoder ) do |res|
  conn.put_copy_data ['a', 123, [5,4,3]]
end

This inserts a single row into copytable with type casts from ruby to database types.

Instance Method Summary

• #initialize(connection) ⇒ BasicTypeMapBasedOnResult constructor

  A new instance of BasicTypeMapBasedOnResult.

Methods included from BasicTypeRegistry

alias_type, register_coder, register_type

Methods inherited from TypeMapByOid

#add_coder, #build_column_map, #coders, #max_rows_for_online_lookup, #max_rows_for_online_lookup=, #rm_coder

Methods included from TypeMap::DefaultTypeMappable

#default_type_map, #default_type_map=, #with_default_type_map

Constructor Details

#initialize(connection) ⇒ BasicTypeMapBasedOnResult

Returns a new instance of BasicTypeMapBasedOnResult.

# File 'lib/pg/basic_type_mapping.rb', line 370

def initialize(connection)
	@coder_maps = build_coder_maps(connection)

	# Populate TypeMapByOid hash with encoders
	@coder_maps.map{|f| f[:encoder].coders }.flatten.each do |coder|
		add_coder(coder)
	end
end