- When explicit sequence execution derives the name

of the auto-generated sequence of a SERIAL column,
which currently only occurs if implicit_returning=False,
now accommodates if the table + column name is greater
than 63 characters using the same logic Postgresql uses.
[ticket:1083]

1 files changed, 14 insertions, 5 deletions

diff --git a/lib/sqlalchemy/dialects/postgresql/base.py b/lib/sqlalchemy/dialects/postgresql/base.py
index 4e7e114c9..22d269cdf 100644
--- a/lib/sqlalchemy/dialects/postgresql/base.py
+++ b/lib/sqlalchemy/dialects/postgresql/base.py
@@ -706,14 +706,23 @@ class PGExecutionContext(default.DefaultExecutionContext):
                 # execute the sequence associated with a SERIAL primary 
                 # key column. for non-primary-key SERIAL, the ID just
                 # generates server side.
-                sch = column.table.schema
 
+                try:
+                    seq_name = column._postgresql_seq_name
+                except AttributeError:
+                    tab = column.table.name 
+                    col = column.name 
+                    tab = tab[0:29 + max(0, (29 - len(col)))] 
+                    col = col[0:29 + max(0, (29 - len(tab)))] 
+                    column._postgresql_seq_name = seq_name = "%s_%s_seq" % (tab, col)
+
+                sch = column.table.schema
                 if sch is not None:
-                    exc = "select nextval('\"%s\".\"%s_%s_seq\"')" % \
-                            (sch, column.table.name, column.name)
+                    exc = "select nextval('\"%s\".\"%s\"')" % \
+                            (sch, seq_name)
                 else:
-                    exc = "select nextval('\"%s_%s_seq\"')" % \
-                            (column.table.name, column.name)
+                    exc = "select nextval('\"%s\"')" % \
+                            (seq_name, )
 
                 return self._execute_scalar(exc, column.type)