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📚 pg backend technical design & clarifications

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Mars Hall 2018-10-14 12:34:34 -07:00 committed by Mars Hall
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website/docs/backends/types/pg.html.md
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# pg # pg
**Kind: Standard with locking** **Kind: Standard (with locking)**
Stores the state in a [Postgres database](https://www.postgresql.org) using two tables, `states` and `locks`. Stores the state in a [Postgres database](https://www.postgresql.org) version 9.5 or newer.
Supports Postgres version 10 and newer. This backend supports [state locking](/docs/state/locking.html).
## Example Configuration ## Example Configuration
@ -24,18 +24,13 @@ terraform {
} }
``` ```
This assumes we have a database created called `terraform_backend`. The Before initializing the backend with `terraform init`, the database must already exist.
Terraform state is stored in a self-managed schema, by default
`terraform_remote_backend`.
Note that for the access credentials we recommend using a We recommend using a [partial configuration](/docs/backends/config.html#partial-configuration) for the `conn_str` variable, because it typically contains access credentials that should not be committed to source control.
[partial configuration](/docs/backends/config.html).
## Using the pg remote state ## Example Referencing
To make use of the pg remote state we can use the To make use of the pg remote state we can use the [`terraform_remote_state` data source](/docs/providers/terraform/d/remote_state.html).
[`terraform_remote_state` data
source](/docs/providers/terraform/d/remote_state.html).
```hcl ```hcl
data "terraform_remote_state" "network" { data "terraform_remote_state" "network" {
@ -46,24 +41,28 @@ data "terraform_remote_state" "network" {
} }
``` ```
The `terraform_remote_state` data source will return all of the root module ## Configuration Variables
outputs defined in the referenced remote state (but not any outputs from
nested modules unless they are explicitly output again in the root). An
example output might look like:
```
data.terraform_remote_state.network:
id = 2018-10-11 01:57:59.780010914 +0000 UTC
backend = pg
config.% = 1
config.conn_str = postgres://localhost/terraform_backend
```
## Configuration variables
The following configuration options or environment variables are supported: The following configuration options or environment variables are supported:
* `conn_str` - (Required) Postgres connection string; a `postgres://` URL * `conn_str` - (Required) Postgres connection string; a `postgres://` URL
* `lock` - Use locks to synchronize state access, default `true` * `lock` - Use locks to synchronize state access, default `true`
* `schema_name` - Name of the automatically managed Postgres schema to store locks & state. * `schema_name` - Name of the automatically-managed Postgres schema to store locks & state, default `terraform_remote_backend`.
## Technical Design
Postgres version 9.5 or newer is required to support the "ON CONFLICT" upsert syntax and *jsonb* data type.
This backend creates two tables, **states** and **locks**, in the automatically-managed Postgres schema configured by the `schema_name` variable.
Both tables are keyed by the [workspace](/docs/state/workspaces.html) name. If workspaces are not in use, the name `default` is used.
The **states** table contains:
* the workspace `name` key as *text* with a unique index
* the Terraform state `data` JSON as *text*.
The **locks** table contains:
* the workspace `name` key as *text* with a unique index
* the lock's `info` JSON as *jsonb*.