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236 lines
8.9 KiB
Markdown
236 lines
8.9 KiB
Markdown
# PostgreSQL database details
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Zulip supports a range of PostgreSQL versions:
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```{include} postgresql-support-table.md
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```
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We recommend that installations [upgrade to the latest
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PostgreSQL][upgrade-postgresql] supported by their version of Zulip.
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[upgrade-postgresql]: upgrade.md#upgrading-postgresql
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## Separate PostgreSQL database
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It is possible to run Zulip against a PostgreSQL database which is not on the
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primary application server. There are two possible flavors of this -- using a
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managed PostgreSQL instance from a cloud provider, or separating the PostgreSQL
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server onto a separate (but still Zulip-managed) server for scaling purposes.
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### Cloud-provider-managed PostgreSQL (e.g., Amazon RDS)
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You can use a database-as-a-service like Amazon RDS for the Zulip database. The
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experience is slightly degraded, in that most providers don't include useful
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dictionary files in their installations, and don't provide a way to provide them
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yourself, resulting in a degraded [full-text search][fts] experience around
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issues dictionary files are relevant (e.g., stemming).
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[fts]: ../subsystems/full-text-search.md
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#### Step 1: Set up Zulip
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Follow the [standard install instructions](install.md), with modified `install`
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arguments:
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```bash
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./zulip-server-*/scripts/setup/install --certbot \
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--email=YOUR_EMAIL --hostname=YOUR_HOSTNAME \
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--puppet-classes=zulip::profile::standalone_nodb,zulip::process_fts_updates \
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--postgresql-missing-dictionaries
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```
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#### Step 2: Create the PostgreSQL database
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Access an administrative `psql` shell on your PostgreSQL database, and
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run the commands in `scripts/setup/create-db.sql` to:
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- Create a database called `zulip` with `C.UTF-8` collation.
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- Create a user called `zulip` with full rights on that database.
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- Log in with the `zulip` user to create a schema called `zulip` in the `zulip`
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database. You might have to grant `create` privileges first for the `zulip`
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user to do this.
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If you cannot run that SQL directly, you should perform the equivalent actions
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in the service's web UI.
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Depending on how authentication works for your PostgreSQL installation, you may
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also need to set a password for the Zulip user, generate a client certificate,
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or similar; consult the documentation for your database provider for the
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available options.
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#### Step 3: Configure Zulip to use the PostgreSQL database
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In `/etc/zulip/settings.py` on your Zulip server, configure the
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following settings with details for how to connect to your PostgreSQL
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server. Your database provider should provide these details.
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- `REMOTE_POSTGRES_HOST`: Name or IP address of the PostgreSQL server.
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- `REMOTE_POSTGRES_PORT`: Port on the PostgreSQL server.
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- `REMOTE_POSTGRES_SSLMODE`: [SSL Mode][ssl-mode] used to connect to the server.
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[ssl-mode]: https://www.postgresql.org/docs/current/libpq-ssl.html#LIBPQ-SSL-PROTECTION
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If you're using password authentication, you should specify the
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password of the `zulip` user in /etc/zulip/zulip-secrets.conf as
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follows:
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```ini
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postgres_password = abcd1234
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```
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Set the remote server's PostgreSQL version in `/etc/zulip/zulip.conf`:
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```ini
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[postgresql]
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# Set this to match the version running on your remote PostgreSQL server
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version = 17
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```
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Now complete the installation by running the following commands.
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```bash
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# Ask Zulip installer to initialize the PostgreSQL database.
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su zulip -c '/home/zulip/deployments/current/scripts/setup/initialize-database'
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# And then generate a realm creation link:
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su zulip -c '/home/zulip/deployments/current/manage.py generate_realm_creation_link'
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```
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### Remote PostgreSQL database
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This assumes two servers; one hosting the PostgreSQL database, and one hosting
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the remainder of the Zulip services.
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#### Step 1: Set up Zulip
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Follow the [standard install instructions](install.md), with modified `install`
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arguments:
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```bash
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./zulip-server-*/scripts/setup/install --certbot \
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--email=YOUR_EMAIL --hostname=YOUR_HOSTNAME \
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--puppet-classes=zulip::profile::standalone_nodb
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```
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#### Step 2: Create the PostgreSQL database server
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On the host that will run PostgreSQL, download the Zulip tarball and install
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just the PostgreSQL server part:
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```bash
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./zulip-server-*/scripts/setup/install \
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--puppet-classes=zulip::profile::postgresql
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./zulip-server-*/scripts/setup/create-database
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```
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You will need to [configure `/etc/postgresql/*/main/pg_hba.conf`][pg-hba] to
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allow connections to the `zulip` database as the `zulip` user from the
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application frontend host. How you configure this is up to you (i.e. password
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authentication, certificates, etc), and is outside the scope of this document.
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[pg-hba]: https://www.postgresql.org/docs/current/auth-pg-hba-conf.html
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#### Step 3: Configure Zulip to use the PostgreSQL database
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In `/etc/zulip/settings.py` on your Zulip server, configure the following
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settings with details for how to connect to your PostgreSQL server.
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- `REMOTE_POSTGRES_HOST`: Name or IP address of the PostgreSQL server.
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- `REMOTE_POSTGRES_PORT`: Port on the PostgreSQL server; this is likely `5432`
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- `REMOTE_POSTGRES_SSLMODE`: [SSL Mode][ssl-mode] used to connect to the server.
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If you're using password authentication, you should specify the
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password of the `zulip` user in /etc/zulip/zulip-secrets.conf as
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follows:
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```ini
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postgres_password = abcd1234
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```
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Set the remote server's PostgreSQL version in `/etc/zulip/zulip.conf`:
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```ini
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[postgresql]
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# Set this to match the version running on your remote PostgreSQL server
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version = 17
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```
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Now complete the installation by running the following commands.
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```bash
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# Ask Zulip installer to initialize the PostgreSQL database.
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su zulip -c '/home/zulip/deployments/current/scripts/setup/initialize-database'
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# And then generate a realm creation link:
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su zulip -c '/home/zulip/deployments/current/manage.py generate_realm_creation_link'
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```
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## PostgreSQL warm standby
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Zulip's configuration allows for [warm standby database replicas][warm-standby]
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as a disaster recovery solution; see the linked PostgreSQL documentation for
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details on this type of deployment. Zulip's configuration can, but is not
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required to, build on top of `wal-g`, our [streaming database backup
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solution][wal-g], for ease of establishing base images without incurring load on
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the primary.
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Warm standby replicas should configure the hostname of their primary replica,
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and username to use for replication, in `/etc/zulip/zulip.conf`:
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```ini
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[postgresql]
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replication_user = replicator
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replication_primary = hostname-of-primary.example.com
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```
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The `postgres` user on the replica will need to be able to authenticate as the
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`replication_user` user, which may require further configuration of
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`pg_hba.conf` and client certificates on the replica. If you are using password
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authentication, you can set a `postgresql_replication_password` secret in
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`/etc/zulip/zulip-secrets.conf`.
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Use `zulip-puppet-apply` to rebuild the PostgreSQL configuration with those
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values. If [wal-g][wal-g] is used, use `env-wal-g backup-fetch` to fetch the
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latest copy of the base backup; otherwise, use [`pg_basebackup`][pg_basebackup].
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The PostgreSQL replica should then begin live-replicating from the primary.
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In the event of a primary failure, use [`pg_ctl promote`][promote] on the warm
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standby to promote it to primary. As with all database promotions, care should
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be taken to ensure that the old primary cannot come back online, and leave the
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cluster with two diverging timelines.
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To make fail-over to the warm-standby faster, without requiring a restart of
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Zulip services, you can configure Zulip with a comma-separated list of remote
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PostgreSQL servers to connect to; it will choose the first which accepts writes
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(i.e. is not a read-only replica). In the event that the primary fails, it will
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repeatedly retry the list, in order, until the replica is promoted and becomes
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writable. To configure this, in `/etc/zulip/settings.py`, set:
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```python3
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REMOTE_POSTGRES_HOST = 'primary-database-host,warm-standby-host'
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```
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[warm-standby]: https://www.postgresql.org/docs/current/warm-standby.html
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[wal-g]: export-and-import.md#database-only-backup-tools
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[pg_basebackup]: https://www.postgresql.org/docs/current/app-pgbasebackup.html
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[promote]: https://www.postgresql.org/docs/current/app-pg-ctl.html
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## PostgreSQL vacuuming alerts
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The `autovac_freeze` PostgreSQL alert from `check_postgres` is particularly
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important. This alert indicates that the age (in terms of number of
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transactions) of the oldest transaction id (XID) is getting close to the
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`autovacuum_freeze_max_age` setting. When the oldest XID hits that age,
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PostgreSQL will force a VACUUM operation, which can often lead to sudden
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downtime until the operation finishes. If it did not do this and the age of the
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oldest XID reached 2 billion, transaction id wraparound would occur and there
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would be data loss. To clear the nagios alert, perform a `VACUUM` in each
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indicated database as a database superuser (i.e. `postgres`).
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See [the PostgreSQL documentation][vacuum] for more details on PostgreSQL
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vacuuming.
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[vacuum]: http://www.postgresql.org/docs/current/static/routine-vacuuming.html#VACUUM-FOR-WRAPAROUND
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