More docs

db.go

@@ -47,13 +47,15 @@ func (db *DB) Options() *Options {
 	return db.opt
 }
 
+// Context returns DB context.
 func (db *DB) Context() context.Context {
 	if db.ctx != nil {
 		return db.ctx
 	}
 	return context.Background()
 }
 
+// WithContext copies the DB, sets context and returns copied DB.
 func (db *DB) WithContext(ctx context.Context) *DB {
 	return &DB{
 		opt:   db.opt,

error.go

@@ -7,7 +7,12 @@ import (
 	"github.com/go-pg/pg/internal"
 )
 
+// ErrNoRows is returned by QueryOne and ExecOne when query returned zero rows
+// but at least one row is expected.
 var ErrNoRows = internal.ErrNoRows
+
+// ErrMultiRows is returned by QueryOne and ExecOne when query returned
+// multiple rows but exactly one row is expected.
 var ErrMultiRows = internal.ErrMultiRows
 
 // Error represents an error returned by PostgreSQL server

orm/query.go

@@ -158,8 +158,14 @@ func (q *Query) TableExpr(expr string, params ...interface{}) *Query {
 	return q
 }
 
-// Column adds column to the Query quoting it according to PostgreSQL rules.
-// ColumnExpr can be used to bypass quoting restriction.
+// Column adds a column to the Query quoting it according to PostgreSQL rules.
+// ColumnExpr can be used to bypass quoting restriction. Column name can be:
+//   - column_name,
+//   - table_alias.column_name,
+//   - table_alias.*,
+//   - RelationName,
+//   - RelationName.column_name,
+//   - RelationName._ to join relation without selecting relation data.
 func (q *Query) Column(columns ...string) *Query {
 	for _, column := range columns {
 		if column == "_" {