Add field_name_type setter and getter to PG::Connection

It allows to set the field name type on a connection scope.

Added methods are:
    * PG::Connection#field_name_type=
    * PG::Connection#field_name_type

ext/pg.h

@@ -102,6 +102,8 @@ typedef struct {
 	VALUE decoder_for_get_copy_data;
 	/* Ruby encoding index of the client/internal encoding */
 	int enc_idx : PG_ENC_IDX_BITS;
+	/* flags controlling Symbol/String field names */
+	unsigned int flags : 2;
 
 #if defined(_WIN32)
 	/* File descriptor to be used for rb_w32_unwrap_io_handle() */
@@ -168,6 +170,10 @@ typedef VALUE (* t_pg_typecast_result)(t_typemap *, VALUE, int, int);
 typedef t_pg_coder *(* t_pg_typecast_query_param)(t_typemap *, VALUE, int);
 typedef VALUE (* t_pg_typecast_copy_get)( t_typemap *, VALUE, int, int, int );
 
+#define PG_RESULT_FIELD_NAMES_MASK 0x03
+#define PG_RESULT_FIELD_NAMES_SYMBOL 0x01
+#define PG_RESULT_FIELD_NAMES_STATIC_SYMBOL 0x02
+
 #define PG_CODER_TIMESTAMP_DB_UTC 0x0
 #define PG_CODER_TIMESTAMP_DB_LOCAL 0x1
 #define PG_CODER_TIMESTAMP_APP_UTC 0x0

ext/pg_connection.c

@@ -13,6 +13,7 @@
 VALUE rb_cPGconn;
 static ID s_id_encode;
 static VALUE sym_type, sym_format, sym_value;
+static VALUE sym_symbol, sym_string, sym_static_symbol;
 
 static PQnoticeReceiver default_notice_receiver = NULL;
 static PQnoticeProcessor default_notice_processor = NULL;
@@ -4060,6 +4061,58 @@ pgconn_decoder_for_get_copy_data_get(VALUE self)
 	return this->decoder_for_get_copy_data;
 }
 
+/*
+ * call-seq:
+ *    conn.field_name_type = Symbol
+ *
+ * Set default type of field names of results retrieved by this connection.
+ * It can be set to one of:
+ * * +:string+ to use String based field names
+ * * +:symbol+ to use Symbol based field names
+ *
+ * The default is +:string+ .
+ *
+ * Settings the type of field names affects only future results.
+ *
+ * See further description at PG::Result#field_name_type=
+ *
+ */
+static VALUE
+pgconn_field_name_type_set(VALUE self, VALUE sym)
+{
+	t_pg_connection *this = pg_get_connection( self );
+
+	this->flags &= ~PG_RESULT_FIELD_NAMES_MASK;
+	if( sym == sym_symbol ) this->flags |= PG_RESULT_FIELD_NAMES_SYMBOL;
+	else if ( sym == sym_static_symbol ) this->flags |= PG_RESULT_FIELD_NAMES_STATIC_SYMBOL;
+	else if ( sym == sym_string );
+	else rb_raise(rb_eArgError, "invalid argument %+"PRIsVALUE, sym);
+
+	return sym;
+}
+
+/*
+ * call-seq:
+ *    conn.field_name_type -> Symbol
+ *
+ * Get type of field names.
+ *
+ * See description at #field_name_type=
+ */
+static VALUE
+pgconn_field_name_type_get(VALUE self)
+{
+	t_pg_connection *this = pg_get_connection( self );
+
+	if( this->flags & PG_RESULT_FIELD_NAMES_SYMBOL ){
+		return sym_symbol;
+	} else if( this->flags & PG_RESULT_FIELD_NAMES_STATIC_SYMBOL ){
+		return sym_static_symbol;
+	} else {
+		return sym_string;
+	}
+}
+
 
 /*
  * Document-class: PG::Connection
@@ -4071,6 +4124,9 @@ init_pg_connection()
 	sym_type = ID2SYM(rb_intern("type"));
 	sym_format = ID2SYM(rb_intern("format"));
 	sym_value = ID2SYM(rb_intern("value"));
+	sym_string = ID2SYM(rb_intern("string"));
+	sym_symbol = ID2SYM(rb_intern("symbol"));
+	sym_static_symbol = ID2SYM(rb_intern("static_symbol"));
 
 	rb_cPGconn = rb_define_class_under( rb_mPG, "Connection", rb_cObject );
 	rb_include_module(rb_cPGconn, rb_mPGconstants);
@@ -4255,4 +4311,7 @@ init_pg_connection()
 	rb_define_method(rb_cPGconn, "encoder_for_put_copy_data", pgconn_encoder_for_put_copy_data_get, 0);
 	rb_define_method(rb_cPGconn, "decoder_for_get_copy_data=", pgconn_decoder_for_get_copy_data_set, 1);
 	rb_define_method(rb_cPGconn, "decoder_for_get_copy_data", pgconn_decoder_for_get_copy_data_get, 0);
+
+	rb_define_method(rb_cPGconn, "field_name_type=", pgconn_field_name_type_set, 1 );
+	rb_define_method(rb_cPGconn, "field_name_type", pgconn_field_name_type_get, 0 );
 }

ext/pg_result.c

@@ -6,10 +6,6 @@
 
 #include "pg.h"
 
-#define PG_RESULT_FIELD_NAMES_MASK 0x03
-#define PG_RESULT_FIELD_NAMES_SYMBOL 0x01
-#define PG_RESULT_FIELD_NAMES_STATIC_SYMBOL 0x02
-
 VALUE rb_cPGresult;
 static VALUE sym_symbol, sym_string, sym_static_symbol;
 
@@ -206,6 +202,7 @@ pg_new_result2(PGresult *result, VALUE rb_pgconn)
 		this->enc_idx = p_conn->enc_idx;
 		this->typemap = p_typemap->funcs.fit_to_result( typemap, self );
 		this->p_typemap = DATA_PTR( this->typemap );
+		this->flags = p_conn->flags;
 	} else {
 		this->enc_idx = rb_locale_encindex();
 	}
@@ -1504,7 +1501,7 @@ pgresult_stream_each_tuple(VALUE self)
  * * +:symbol+ to use Symbol based field names
  * * +:static_symbol+ to use pinned Symbol (can not be garbage collected) - Don't use this, it will probably removed in future.
  *
- * The default is +:string+ .
+ * The default is retrieved from PG::Connection#field_name_type , which defaults to +:string+ .
  *
  * This setting affects several result methods:
  * * keys of Hash returned by #[] , #each and #stream_each

spec/pg/connection_spec.rb

@@ -1824,6 +1824,35 @@
 		end
 	end
 
+	describe :field_name_type do
+		it "uses string field names per default" do
+			conn = PG.connect( @conninfo )
+			expect(conn.field_name_type).to eq(:string)
+			conn.finish
+		end
+
+		it "can set string field names" do
+			@conn.field_name_type = :string
+			expect(@conn.field_name_type).to eq(:string)
+			res = @conn.exec("SELECT 1 as az")
+			expect(res.field_name_type).to eq(:string)
+			expect(res.fields).to eq(["az"])
+		end
+
+		it "can set symbol field names" do
+			@conn.field_name_type = :symbol
+			expect(@conn.field_name_type).to eq(:symbol)
+			res = @conn.exec("SELECT 1 as az")
+			expect(res.field_name_type).to eq(:symbol)
+			expect(res.fields).to eq([:az])
+		end
+
+		it "can't set invalid values" do
+			expect{ @conn.field_name_type = :sym }.to raise_error(ArgumentError, /invalid argument :sym/)
+			expect{ @conn.field_name_type = "symbol" }.to raise_error(ArgumentError, /invalid argument "symbol"/)
+		end
+	end
+
 	describe "deprecated forms of methods" do
 		it "should forward exec to exec_params" do
 			res = @conn.exec("VALUES($1::INT)", [7]).values