Fixed #4432 -- Fixed PostgreSQL sequence resetting in the case when a table has

no rows yet. Thanks, mrmachine.


git-svn-id: http://code.djangoproject.com/svn/django/trunk@5455 bcc190cf-cafb-0310-a4f2-bffc1f526a37

3 files changed, 19 insertions, 8 deletions

diff --git a/AUTHORS b/AUTHORS
index bff482f294..01f7983e36 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -170,6 +170,7 @@ answer newbie questions, and generally made Django that much better:
     mitakummaa@gmail.com
     mmarshall
     Eric Moritz <http://eric.themoritzfamily.com/>
+    mrmachine <real.human@mrmachine.net>
     Robin Munn <http://www.geekforgod.com/>
     Robert Myers <myer0052@gmail.com>
     Nebojša Dorđević
diff --git a/django/db/backends/postgresql/base.py b/django/db/backends/postgresql/base.py
index a5b38a883d..fedbb6b7f1 100644
--- a/django/db/backends/postgresql/base.py
+++ b/django/db/backends/postgresql/base.py
@@ -219,22 +219,27 @@ def get_sql_sequence_reset(style, model_list):
     from django.db import models
     output = []
     for model in model_list:
+        # Use `coalesce` to set the sequence for each model to the max pk value if there are records,
+        # or 1 if there are none. Set the `is_called` property (the third argument to `setval`) to true
+        # if there are records (as the max pk value is already in use), otherwise set it to false.
         for f in model._meta.fields:
             if isinstance(f, models.AutoField):
-                output.append("%s setval('%s', (%s max(%s) %s %s));" % \
+                output.append("%s setval('%s', coalesce(max(%s), 1), max(%s) %s null) %s %s;" % \
                     (style.SQL_KEYWORD('SELECT'),
                     style.SQL_FIELD(quote_name('%s_%s_seq' % (model._meta.db_table, f.column))),
-                    style.SQL_KEYWORD('SELECT'),
                     style.SQL_FIELD(quote_name(f.column)),
+                    style.SQL_FIELD(quote_name(f.column)),
+                    style.SQL_KEYWORD('IS NOT'),
                     style.SQL_KEYWORD('FROM'),
                     style.SQL_TABLE(quote_name(model._meta.db_table))))
                 break # Only one AutoField is allowed per model, so don't bother continuing.
         for f in model._meta.many_to_many:
-            output.append("%s setval('%s', (%s max(%s) %s %s));" % \
+            output.append("%s setval('%s', coalesce(max(%s), 1), max(%s) %s null) %s %s;" % \
                 (style.SQL_KEYWORD('SELECT'),
                 style.SQL_FIELD(quote_name('%s_id_seq' % f.m2m_db_table())),
-                style.SQL_KEYWORD('SELECT'),
                 style.SQL_FIELD(quote_name('id')),
+                style.SQL_FIELD(quote_name('id')),
+                style.SQL_KEYWORD('IS NOT'),
                 style.SQL_KEYWORD('FROM'),
                 style.SQL_TABLE(f.m2m_db_table())))
     return output
diff --git a/django/db/backends/postgresql_psycopg2/base.py b/django/db/backends/postgresql_psycopg2/base.py
index 9898b121f4..d9ad363ac1 100644
--- a/django/db/backends/postgresql_psycopg2/base.py
+++ b/django/db/backends/postgresql_psycopg2/base.py
@@ -176,22 +176,27 @@ def get_sql_sequence_reset(style, model_list):
     from django.db import models
     output = []
     for model in model_list:
+        # Use `coalesce` to set the sequence for each model to the max pk value if there are records,
+        # or 1 if there are none. Set the `is_called` property (the third argument to `setval`) to true
+        # if there are records (as the max pk value is already in use), otherwise set it to false.
         for f in model._meta.fields:
             if isinstance(f, models.AutoField):
-                output.append("%s setval('%s', (%s max(%s) %s %s));" % \
+                output.append("%s setval('%s', coalesce(max(%s), 1), max(%s) %s null) %s %s;" % \
                     (style.SQL_KEYWORD('SELECT'),
                     style.SQL_FIELD(quote_name('%s_%s_seq' % (model._meta.db_table, f.column))),
-                    style.SQL_KEYWORD('SELECT'),
                     style.SQL_FIELD(quote_name(f.column)),
+                    style.SQL_FIELD(quote_name(f.column)),
+                    style.SQL_KEYWORD('IS NOT'),
                     style.SQL_KEYWORD('FROM'),
                     style.SQL_TABLE(quote_name(model._meta.db_table))))
                 break # Only one AutoField is allowed per model, so don't bother continuing.
         for f in model._meta.many_to_many:
-            output.append("%s setval('%s', (%s max(%s) %s %s));" % \
+            output.append("%s setval('%s', coalesce(max(%s), 1), max(%s) %s null) %s %s;" % \
                 (style.SQL_KEYWORD('SELECT'),
                 style.SQL_FIELD(quote_name('%s_id_seq' % f.m2m_db_table())),
-                style.SQL_KEYWORD('SELECT'),
                 style.SQL_FIELD(quote_name('id')),
+                style.SQL_FIELD(quote_name('id')),
+                style.SQL_KEYWORD('IS NOT'),
                 style.SQL_KEYWORD('FROM'),
                 style.SQL_TABLE(f.m2m_db_table())))
     return output