class PG::BasicTypeMapForResults

See also PG::BasicTypeMapBasedOnResult for the encoder direction and PG::BasicTypeRegistry for the definition of additional types.
[“a”, 123, 2023-03-19 18:39:44 UTC]
This prints the rows with type casted columns:
end
end
p row
while row=conn.get_copy_data
conn.copy_data( “COPY copytable TO STDOUT WITH (FORMAT binary)”, row_decoder ) do |res|
row_decoder = PG::BinaryDecoder::CopyRow.new type_map: tm
tm = btm.build_column_map( res )
# Build a PG::TypeMapByColumn with decoders suitable for copytable.
btm = PG::BasicTypeMapForResults.new(conn)
# Build a type map for common database to ruby type decoders.
res = conn.exec_params( “SELECT * FROM copytable LIMIT 0”, [], 1 )
# Retrieve table OIDs per empty result set in binary format.
conn.exec( “CREATE TABLE copytable AS VALUES(‘a’, 123, ‘2023-03-19 18:39:44’::TIMESTAMP)” )
Very similar with binary format:
[“a”, 123, [5, 4, 3]]
This prints the rows with type casted columns:
end
end
p row
while row=conn.get_copy_data
conn.copy_data( “COPY copytable TO STDOUT”, row_decoder ) do |res|
row_decoder = PG::TextDecoder::CopyRow.new type_map: tm
tm = btm.build_column_map( res )
# Build a PG::TypeMapByColumn with decoders suitable for copytable.
btm = PG::BasicTypeMapForResults.new(conn)
# Build a type map for common database to ruby type decoders.
res = conn.exec( “SELECT * FROM copytable LIMIT 0” )
# Retrieve table OIDs per empty result set.
conn.exec( “CREATE TABLE copytable AS VALUES(‘a’, 123, ‘{5,4,3}’::INT[])” )
For the following table:
to cast #get_copy_data fields:
a result independent PG::TypeMapByColumn type map, which can subsequently be used
PG::TypeMapByOid#build_column_map(result) can be used to generate
res.values # => [[5]]
# is done by PG::TextDecoder::Integer internally for all value retrieval methods.
# Retrieve and cast the result value. Value format is 0 (text) and OID is 20. Therefore typecasting
res = conn.exec_params( “SELECT $1::INT”, [‘5’] )
# Execute a query.
conn.type_map_for_results = PG::BasicTypeMapForResults.new(conn)
# Assign a default ruleset for type casts of output values.
conn = PG::Connection.new
Example:
own set of rules to choose suitable encoders and decoders.
Higher level libraries will most likely not make use of this class, but use their
Result values are type casted based on the type OID of the given result column.
PostgreSQL’s pg_type table in PG::BasicTypeMapForResults.new .
OIDs of supported type casts are not hard-coded in the sources, but are retrieved from the
Simple set of rules for type casting common PostgreSQL types to Ruby.