docs about side-effects in txn_do coderef

diff --git a/lib/DBIx/Class/Storage.pm b/lib/DBIx/Class/Storage.pm
index 9a58b94..3369069 100644 (file)
--- a/lib/DBIx/Class/Storage.pm
+++ b/lib/DBIx/Class/Storage.pm
@@ -169,6 +169,15 @@ In a nested transaction (calling txn_do() from within a txn_do() coderef) only
 the outermost transaction will issue a L</txn_commit>, and txn_do() can be
 called in void, scalar and list context and it will behave as expected.
 
+Please note that all of the code in your coderef, including non-DBIx::Class
+code, is part of a transaction.  This transaction may fail out halfway, or
+it may get partially double-executed (in the case that our DB connection
+failed halfway through the transaction, in which case we reconnect and
+restart the txn).  Therefore it is best that any side-effects in your coderef
+are idempotent (that is, can be re-executed multiple times and get the
+same result), and that you check up on your side-effects in the case of
+transaction failure.
+
 =cut
 
 sub txn_do {