Databases ¶

Django attempts to support as many features as possible on all database backends. However, not all database backends are alike, and we’ve had to make design decisions on which features to support and which assumptions we can make safely.

This file describes some of the features that might be relevant to Django usage. Of course, it is not intended as a replacement for server-specific documentation or reference manuals.

General notes ¶

Persistent connections ¶

Persistent connections avoid the overhead of re-establishing a connection to the database in each request. They’re controlled by the CONN_MAX_AGE parameter which defines the maximum lifetime of a connection. It can be set independently for each database.

The default value is 0 , preserving the historical behavior of closing the database connection at the end of each request. To enable persistent connections, set CONN_MAX_AGE to a positive number of seconds. For unlimited persistent connections, set it to None .

Connection management ¶

Django opens a connection to the database when it first makes a database query. It keeps this connection open and reuses it in subsequent requests. Django closes the connection once it exceeds the maximum age defined by CONN_MAX_AGE or when it isn’t usable any longer.

In detail, Django automatically opens a connection to the database whenever it needs one and doesn’t have one already — either because this is the first connection, or because the previous connection was closed.

At the beginning of each request, Django closes the connection if it has reached its maximum age. If your database terminates idle connections after some time, you should set CONN_MAX_AGE to a lower value, so that Django doesn’t attempt to use a connection that has been terminated by the database server. (This problem may only affect very low traffic sites.)

At the end of each request, Django closes the connection if it has reached its maximum age or if it is in an unrecoverable error state. If any database errors have occurred while processing the requests, Django checks whether the connection still works, and closes it if it doesn’t. Thus, database errors affect at most one request; if the connection becomes unusable, the next request gets a fresh connection.

Caveats ¶

Since each thread maintains its own connection, your database must support at least as many simultaneous connections as you have worker threads.

Sometimes a database won’t be accessed by the majority of your views, for example because it’s the database of an external system, or thanks to caching. In such cases, you should set CONN_MAX_AGE to a low value or even 0 , because it doesn’t make sense to maintain a connection that’s unlikely to be reused. This will help keep the number of simultaneous connections to this database small.

The development server creates a new thread for each request it handles, negating the effect of persistent connections. Don’t enable them during development.

When Django establishes a connection to the database, it sets up appropriate parameters, depending on the backend being used. If you enable persistent connections, this setup is no longer repeated every request. If you modify parameters such as the connection’s isolation level or time zone, you should either restore Django’s defaults at the end of each request, force an appropriate value at the beginning of each request, or disable persistent connections.

Encoding ¶

Django assumes that all databases use UTF-8 encoding. Using other encodings may result in unexpected behavior such as “value too long” errors from your database for data that is valid in Django. See the database specific notes below for information on how to set up your database correctly.

PostgreSQL notes ¶

Django supports PostgreSQL 8.4 and higher.

PostgreSQL connection settings ¶

See HOST for details.

Optimizing PostgreSQL’s configuration ¶

Django needs the following parameters for its database connections:


    
     client_encoding


    
     'UTF8'


    
     default_transaction_isolation


    
     'read
    
    
     committed'

by default, or the value set in the connection options (see below),


    
     timezone


    
     'UTC'

when


     
      USE_TZ


    
     True

, value of


     
      TIME_ZONE

otherwise.

If these parameters already have the correct values, Django won’t set them for every new connection, which improves performance slightly. You can configure them directly in postgresql.conf or more conveniently per database user with ALTER ROLE .

Django will work just fine without this optimization, but each new connection will do some additional queries to set these parameters.

Autocommit mode ¶

In previous versions of Django, database-level autocommit could be enabled by setting the autocommit key in the OPTIONS part of your database configuration in DATABASES :

DATABASES = {
    # ...
    'OPTIONS': {
        'autocommit': True,
Since Django 1.6, autocommit is turned on by default. This configuration is
ignored and can be safely removed.
Isolation level¶
Like PostgreSQL itself, Django defaults to the READ COMMITTED isolation
level. If you need a higher isolation level such as REPEATABLE READ or
SERIALIZABLE, set it in the OPTIONS part of your database
configuration in DATABASES:
import psycopg2.extensions
DATABASES = {
    # ...
    'OPTIONS': {
        'isolation_level': psycopg2.extensions.ISOLATION_LEVEL_SERIALIZABLE,
Under higher isolation levels, your application should be prepared to
handle exceptions raised on serialization failures. This option is
designed for advanced uses.
Indexes for varchar and text columns¶
When specifying db_index=True on your model fields, Django typically
outputs a single CREATE INDEX statement.  However, if the database type
for the field is either varchar or text (e.g., used by CharField,
FileField, and TextField), then Django will create
an additional index that uses an appropriate PostgreSQL operator class
for the column.  The extra index is necessary to correctly perform
lookups that use the LIKE operator in their SQL, as is done with the
contains and startswith lookup types.
MySQL notes¶
Version support¶
Django supports MySQL 5.0.3 and higher.
Django’s inspectdb feature uses the information_schema database, which
contains detailed data on all database schemas.
The minimum version requirement of MySQL 5.0.3 was set in Django 1.5.
Django expects the database to support Unicode (UTF-8 encoding) and delegates to
it the task of enforcing transactions and referential integrity. It is important
to be aware of the fact that the two latter ones aren’t actually enforced by
MySQL when using the MyISAM storage engine, see the next section.
Storage engines¶
MySQL has several storage engines. You can change the default storage engine
in the server configuration.
Until MySQL 5.5.4, the default engine was MyISAM [1]. The main drawbacks of
MyISAM are that it doesn’t support transactions or enforce foreign-key
constraints. On the plus side, it was the only engine that supported full-text
indexing and searching until MySQL 5.6.4.
Since MySQL 5.5.5, the default storage engine is InnoDB. This engine is fully
transactional and supports foreign key references. It’s probably the best
choice at this point. However, note that the the InnoDB autoincrement counter
is lost on a MySQL restart because it does not remember the
AUTO_INCREMENT value, instead recreating it as “max(id)+1”. This may
result in an inadvertent reuse of AutoField values.
If you upgrade an existing project to MySQL 5.5.5 and subsequently add some
tables, ensure that your tables are using the same storage engine (i.e. MyISAM
vs. InnoDB). Specifically, if tables that have a ForeignKey between them
use different storage engines, you may see an error like the following when
running syncdb:
_mysql_exceptions.OperationalError: (
    1005, "Can't create table '\\db_name\\.#sql-4a8_ab' (errno: 150)"
[1]Unless this was changed by the packager of your MySQL package. We’ve
had reports that the Windows Community Server installer sets up InnoDB as
the default storage engine, for example.
MySQLdb¶
MySQLdb is the Python interface to MySQL. Version 1.2.1p2 or later is
required for full MySQL support in Django.
If you see ImportError: cannot import name ImmutableSet when trying to
use Django, your MySQLdb installation may contain an outdated sets.py
file that conflicts with the built-in module of the same name from Python
2.4 and later. To fix this, verify that you have installed MySQLdb version
1.2.1p2 or newer, then delete the sets.py file in the MySQLdb
directory that was left by an earlier version.
There are known issues with the way MySQLdb converts date strings into
datetime objects. Specifically, date strings with value 0000-00-00 are valid for
MySQL but will be converted into None by MySQLdb.
This means you should be careful while using loaddata/dumpdata with rows
that may have 0000-00-00 values, as they will be converted to None.
Python 3¶
At the time of writing, the latest release of MySQLdb (1.2.4) doesn’t support
Python 3. In order to use MySQL under Python 3, you’ll have to install an
unofficial fork, such as MySQL-for-Python-3.




    

This port is still in alpha. In particular, it doesn’t support binary data,
making it impossible to use django.db.models.BinaryField.
Time zone definitions¶
If you plan on using Django’s timezone support,
use mysql_tzinfo_to_sql to load time zone tables into the MySQL database.
This needs to be done just once for your MySQL server, not per database.
Creating your database¶
You can create your database using the command-line tools and this SQL:
CREATE DATABASE <dbname> CHARACTER SET utf8;
This ensures all tables and columns will use UTF-8 by default.
Collation settings¶
The collation setting for a column controls the order in which data is sorted
as well as what strings compare as equal. It can be set on a database-wide
level and also per-table and per-column. This is documented thoroughly in
the MySQL documentation. In all cases, you set the collation by directly
manipulating the database tables; Django doesn’t provide a way to set this on
the model definition.
By default, with a UTF-8 database, MySQL will use the
utf8_general_ci collation. This results in all string equality
comparisons being done in a case-insensitive manner. That is, "Fred" and
"freD" are considered equal at the database level. If you have a unique
constraint on a field, it would be illegal to try to insert both "aa" and
"AA" into the same column, since they compare as equal (and, hence,
non-unique) with the default collation.
In many cases, this default will not be a problem. However, if you really want
case-sensitive comparisons on a particular column or table, you would change
the column or table to use the utf8_bin collation. The main thing to be
aware of in this case is that if you are using MySQLdb 1.2.2, the database
backend in Django will then return bytestrings (instead of unicode strings) for
any character fields it receive from the database. This is a strong variation
from Django’s normal practice of always returning unicode strings. It is up
to you, the developer, to handle the fact that you will receive bytestrings if
you configure your table(s) to use utf8_bin collation. Django itself should
mostly work smoothly with such columns (except for the contrib.sessions
Session and contrib.admin LogEntry tables described below), but
your code must be prepared to call django.utils.encoding.smart_text() at
times if it really wants to work with consistent data – Django will not do
this for you (the database backend layer and the model population layer are
separated internally so the database layer doesn’t know it needs to make this
conversion in this one particular case).
If you’re using MySQLdb 1.2.1p2, Django’s standard
CharField class will return unicode strings even
with utf8_bin collation. However, TextField
fields will be returned as an array.array instance (from Python’s standard
array module). There isn’t a lot Django can do about that, since, again,
the information needed to make the necessary conversions isn’t available when
the data is read in from the database. This problem was fixed in MySQLdb
1.2.2, so if you want to use TextField with
utf8_bin collation, upgrading to version 1.2.2 and then dealing with the
bytestrings (which shouldn’t be too difficult) as described above is the
recommended solution.
Should you decide to use utf8_bin collation for some of your tables with
MySQLdb 1.2.1p2 or 1.2.2, you should still use utf8_general_ci
(the default) collation for the django.contrib.sessions.models.Session
table (usually called django_session) and the
django.contrib.admin.models.LogEntry table (usually called
django_admin_log). Those are the two standard tables that use
TextField internally.
Please note that according to MySQL Unicode Character Sets, comparisons for
the utf8_general_ci collation are faster, but slightly less correct, than
comparisons for utf8_unicode_ci. If this is acceptable for your application,
you should use utf8_general_ci because it is faster. If this is not acceptable
(for example, if you require German dictionary order), use utf8_unicode_ci
because it is more accurate.
Warning
Model formsets validate unique fields in a case-sensitive manner. Thus when
using a case-insensitive collation, a formset with unique field values that
differ only by case will pass validation, but upon calling save(), an
IntegrityError will be raised.
Connecting to the database¶
Refer to the settings documentation.
Connection settings are used in this order:
OPTIONS.
NAME, USER, PASSWORD,
HOST, PORT
MySQL option files.
In other words, if you set the name of the database in OPTIONS,
this will take precedence over NAME, which would override
anything in a MySQL option file.
Here’s a sample configuration which uses a MySQL option file:
# settings.py
DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.mysql',
        'OPTIONS': {
            'read_default_file': '/path/to/my.cnf',
# my.cnf
[client]
database = NAME
user = USER
password = PASSWORD
default-character-set = utf8
Several other MySQLdb connection options may be useful, such as ssl,
init_command, and sql_mode. Consult the MySQLdb documentation for
more details.
Creating your tables¶
When Django generates the schema, it doesn’t specify a storage engine, so
tables will be created with whatever default storage engine your database
server is configured for. The easiest solution is to set your database server’s
default storage engine to the desired engine.
If you’re using a hosting service and can’t change your server’s default
storage engine, you have a couple of options.
After the tables are created, execute an ALTER TABLE statement to
convert a table to a new storage engine (such as InnoDB):
ALTER TABLE <tablename> ENGINE=INNODB;
This can be tedious if you have a lot of tables.
Another option is to use the init_command option for MySQLdb prior to
creating your tables:
'OPTIONS': {
   'init_command': 'SET storage_engine=INNODB',
This sets the default storage engine upon connecting to the database.
After your tables have been created, you should remove this option as it
adds a query that is only needed during table creation to each database
connection.
Another method for changing the storage engine is described in
AlterModelOnSyncDB.
Table names¶
There are known issues in even the latest versions of MySQL that can cause the
case of a table name to be altered when certain SQL statements are executed
under certain conditions. It is recommended that you use lowercase table
names, if possible, to avoid any problems that might arise from this behavior.
Django uses lowercase table names when it auto-generates table names from
models, so this is mainly a consideration if you are overriding the table name
via the db_table parameter.
Savepoints¶
Both the Django ORM and MySQL (when using the InnoDB storage engine) support database savepoints.
If you use the MyISAM storage engine please be aware of the fact that you will
receive database-generated errors if you try to use the savepoint-related
methods of the transactions API. The reason
for this is that detecting the storage engine of a MySQL database/table is an
expensive operation so it was decided it isn’t worth to dynamically convert
these methods in no-op’s based in the results of such detection.
Notes on specific fields¶
Character fields¶
Any fields that are stored with VARCHAR column types have their
max_length restricted to 255 characters if you are using unique=True
for the field. This affects CharField,
SlugField and
CommaSeparatedIntegerField.
DateTime fields¶
MySQL does not store fractions of seconds. Fractions of seconds are truncated
to zero when the time is stored.
Row locking with QuerySet.select_for_update()¶
MySQL does not support the NOWAIT option to the SELECT ... FOR UPDATE
statement. If select_for_update() is used with nowait=True then a
DatabaseError will be raised.
Automatic typecasting can cause unexpected results¶
When performing a query on a string type, but with an integer value, MySQL will
coerce the types of all values in the table to an integer before performing the
comparison. If your table contains the values 'abc'




    
, 'def' and you
query for WHERE mycolumn=0, both rows will match. Similarly, WHERE mycolumn=1
will match the value 'abc1'. Therefore, string type fields included in Django
will always cast the value to a string before using it in a query.
If you implement custom model fields that inherit from Field
directly, are overriding get_prep_value(), or use
extra() or
raw(), you should ensure that you
perform the appropriate typecasting.
SQLite notes¶
SQLite provides an excellent development alternative for applications that
are predominantly read-only or require a smaller installation footprint. As
with all database servers, though, there are some differences that are
specific to SQLite that you should be aware of.
Substring matching and case sensitivity¶
For all SQLite versions, there is some slightly counter-intuitive behavior when
attempting to match some types of strings.  These are triggered when using the
iexact or contains filters in Querysets. The behavior
splits into two cases:
1. For substring matching, all matches are done case-insensitively. That is a
filter such as filter(name__contains="aa") will match a name of "Aabb".
2. For strings containing characters outside the ASCII range, all exact string
matches are performed case-sensitively, even when the case-insensitive options
are passed into the query. So the iexact filter will behave exactly
the same as the exact filter in these cases.
Some possible workarounds for this are documented at sqlite.org, but they
aren’t utilised by the default SQLite backend in Django, as incorporating them
would be fairly difficult to do robustly. Thus, Django exposes the default
SQLite behavior and you should be aware of this when doing case-insensitive or
substring filtering.
SQLite 3.3.6 or newer strongly recommended¶
Versions of SQLite 3.3.5 and older contains the following bugs:
A bug when handling ORDER BY parameters. This can cause problems when
you use the select parameter for the extra() QuerySet method. The bug
can be identified by the error message OperationalError: ORDER BY terms
must not be non-integer constants.
A bug when handling aggregation together with DateFields and
DecimalFields.
SQLite 3.3.6 was released in April 2006, so most current binary distributions
for different platforms include newer version of SQLite usable from Python
through either the pysqlite2 or the sqlite3 modules.
Version 3.5.9¶
The Ubuntu “Intrepid Ibex” (8.10) SQLite 3.5.9-3 package contains a bug that
causes problems with the evaluation of query expressions. If you are using
Ubuntu “Intrepid Ibex”, you will need to update the package to version
3.5.9-3ubuntu1 or newer (recommended) or find an alternate source for SQLite
packages, or install SQLite from source.
At one time, Debian Lenny shipped with the same malfunctioning SQLite 3.5.9-3
package. However the Debian project has subsequently issued updated versions
of the SQLite package that correct these bugs. If you find you are getting
unexpected results under Debian, ensure you have updated your SQLite package
to 3.5.9-5 or later.
The problem does not appear to exist with other versions of SQLite packaged
with other operating systems.
Version 3.6.2¶
SQLite version 3.6.2 (released August 30, 2008) introduced a bug into SELECT
DISTINCT handling that is triggered by, amongst other things, Django’s
DateQuerySet (returned by the dates() method on a queryset).
You should avoid using this version of SQLite with Django. Either upgrade to
3.6.3 (released September 22, 2008) or later, or downgrade to an earlier
version of SQLite.
Using newer versions of the SQLite DB-API 2.0 driver¶
For versions of Python 2.5 or newer that include sqlite3 in the standard
library Django will now use a pysqlite2 interface in preference to
sqlite3 if it finds one is available.
This provides the ability to upgrade both the DB-API 2.0 interface or SQLite 3
itself to versions newer than the ones included with your particular Python
binary distribution, if needed.
“Database is locked” errors¶
SQLite is meant to be a lightweight database, and thus can’t support a high
level of concurrency. OperationalError: database is locked errors indicate
that your application is experiencing more concurrency than sqlite can
handle in default configuration. This error means that one thread or process has
an exclusive lock on the database connection and another thread timed out
waiting for the lock the be released.
Python’s SQLite wrapper has
a default timeout value that determines how long the second thread is allowed to
wait on the lock before it times out and raises the OperationalError: database
is locked error.
If you’re getting this error, you can solve it by:
Switching to another database backend. At a certain point SQLite becomes
too “lite” for real-world applications, and these sorts of concurrency
errors indicate you’ve reached that point.
Rewriting your code to reduce concurrency and ensure that database
transactions are short-lived.
Increase the default timeout value by setting the timeout database
option:
'OPTIONS': {
    # ...
    'timeout': 20,
    # ...
This will simply make SQLite wait a bit longer before throwing “database
is locked” errors; it won’t really do anything to solve them.
QuerySet.select_for_update() not supported¶
SQLite does not support the SELECT ... FOR UPDATE syntax. Calling it will
have no effect.
“pyformat” parameter style in raw queries not supported¶
For most backends, raw queries (Manager.raw() or cursor.execute())
can use the “pyformat” parameter style, where placeholders in the query
are given as '%(name)s' and the parameters are passed as a dictionary
rather than a list. SQLite does not support this.
Parameters not quoted in connection.queries¶
sqlite3 does not provide a way to retrieve the SQL after quoting and
substituting the parameters. Instead, the SQL in connection.queries is
rebuilt with a simple string interpolation. It may be incorrect. Make sure
you add quotes where necessary before copying a query into an SQLite shell.
Oracle notes¶
Django supports Oracle Database Server versions 9i and
higher. Oracle version 10g or later is required to use Django’s
regex and iregex query operators. You will also need at least
version 4.3.1 of the cx_Oracle Python driver.
Note that due to a Unicode-corruption bug in cx_Oracle 5.0, that
version of the driver should not be used with Django;
cx_Oracle 5.0.1 resolved this issue, so if you’d like to use a
more recent cx_Oracle, use version 5.0.1.
cx_Oracle 5.0.1 or greater can optionally be compiled with the
WITH_UNICODE environment variable.  This is recommended but not
required.
In order for the python manage.py syncdb command to work, your Oracle
database user must have privileges to run the following commands:
CREATE TABLE
CREATE SEQUENCE
CREATE PROCEDURE
CREATE TRIGGER
To run Django’s test suite, the user needs these additional privileges:
CREATE USER
DROP USER
CREATE TABLESPACE
DROP TABLESPACE
CONNECT WITH ADMIN OPTION
RESOURCE WITH ADMIN OPTION
The Oracle database backend uses the SYS.DBMS_LOB package, so your user
will require execute permissions on it. It’s normally accessible to all users
by default, but in case it is not, you’ll need to grant permissions like so:
GRANT EXECUTE ON SYS.DBMS_LOB TO user;
Connecting to the database¶
To connect using the service name of your Oracle database, your settings.py
file should look something like this:
DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.oracle',
        'NAME': 'xe',
        'USER': 'a_user',
        'PASSWORD': 'a_password',
        'HOST': '',
        'PORT': '',
In this case, you should leave both HOST and PORT empty.
However, if you don’t use a tnsnames.ora file or a similar naming method
and want to connect using the SID (“xe” in this example), then fill in both
HOST and PORT like so:
DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.oracle',
        'NAME': 'xe',
        'USER': 'a_user',
        'PASSWORD': 'a_password',
        'HOST': 'dbprod01ned.mycompany.com',
        'PORT': '1540',
You should either supply both HOST and PORT, or leave
both as empty strings. Django will use a different connect descriptor depending
on that choice.
Threaded option¶
If you plan to run Django in a multithreaded environment (e.g. Apache using the
default MPM module on any modern operating system), then you must set
the threaded option of your Oracle database configuration to True:
'OPTIONS': {
    'threaded': True,
Failure to do this may result in crashes and other odd behavior.
INSERT ... RETURNING INTO¶
By default, the Oracle backend uses a RETURNING INTO clause to efficiently
retrieve the value of an AutoField when inserting new rows.  This behavior
may result in a DatabaseError in certain unusual setups, such as when
inserting into a remote table, or into a view with an INSTEAD OF trigger.
The RETURNING INTO clause can be disabled by setting the
use_returning_into option of the database configuration to False:
'OPTIONS': {
    'use_returning_into': False,
In this case, the Oracle backend will use a separate SELECT query to
retrieve AutoField values.
Naming issues¶
Oracle imposes a name length limit of 30 characters. To accommodate this, the
backend truncates database identifiers to fit, replacing the final four
characters of the truncated name with a repeatable MD5 hash value.
Additionally, the backend turns database identifiers to all-uppercase.
To prevent these transformations (this is usually required only when dealing
with legacy databases or accessing tables which belong to other users), use
a quoted name as the value for db_table:
class LegacyModel(models.Model):
    class Meta:
        db_table = '"name_left_in_lowercase"'
class ForeignModel(models.Model):
    class Meta:
        db_table = '"OTHER_USER"."NAME_ONLY_SEEMS_OVER_30"'
Quoted names can also be used with Django’s other supported database
backends; except for Oracle, however, the quotes have no effect.
When running syncdb, an ORA-06552 error may be encountered if
certain Oracle keywords are used as the name of a model field or the
value of a db_column option.  Django quotes all identifiers used
in queries to prevent most such problems, but this error can still
occur when an Oracle datatype is used as a column name.  In
particular, take care to avoid using the names date,
timestamp, number or float as a field name.
NULL and empty strings¶
Django generally prefers to use the empty string (‘’) rather than
NULL, but Oracle treats both identically. To get around this, the
Oracle backend ignores an explicit null option on fields that
have the empty string as a possible value and generates DDL as if
null=True. When fetching from the database, it is assumed that
a NULL value in one of these fields really means the empty
string, and the data is silently converted to reflect this assumption.
TextField limitations¶
The Oracle backend stores TextFields as NCLOB columns. Oracle imposes
some limitations on the usage of such LOB columns in general:
LOB columns may not be used as primary keys.
LOB columns may not be used in indexes.
LOB columns may not be used in a SELECT DISTINCT list. This means that
attempting to use the QuerySet.distinct method on a model that
includes TextField columns will result in an error when run against
Oracle. As a workaround, use the QuerySet.defer method in conjunction
with distinct() to prevent TextField columns from being included in
the SELECT DISTINCT list.
Using a 3rd-party database backend¶
In addition to the officially supported databases, there are backends provided
by 3rd parties that allow you to use other databases with Django:
SAP SQL Anywhere
IBM DB2
Microsoft SQL Server
Firebird
ADSDB
The Django versions and ORM features supported by these unofficial backends
vary considerably. Queries regarding the specific capabilities of these
unofficial backends, along with any support queries, should be directed to
the support channels provided by each 3rd party project.
Row locking with QuerySet.select_for_update()
Automatic typecasting can cause unexpected results
SQLite notes
Substring matching and case sensitivity
SQLite 3.3.6 or newer strongly recommended
Version 3.5.9
Version 3.6.2
Using newer versions of the SQLite DB-API 2.0 driver
“Database is locked” errors
QuerySet.select_for_update() not supported
“pyformat” parameter style in raw queries not supported
Parameters not quoted in connection.queries
Oracle notes
Connecting to the database
Threaded option
INSERT ... RETURNING INTO
Naming issues
NULL and empty strings
TextField limitations
Using a 3rd-party database backend