Add driver for pgx v5

Fixes #827

- Move existing driver into database/pgx/v4
- Make exported items into database/pgx into links to database/pgx/v4,
  marked as Deprecated
- Remove most tests in database/pgx, leaving a couple of e2e tests
  behind to help ensure backwards compatibility.
- Mark defunct ErrDatabaseDirty as Deprecated - no code returns it
- Bump pgx/v4 dependency
- Add test runs for newer Postgres versions

README.md

@@ -24,7 +24,8 @@ Forked from [mattes/migrate](https://github.com/mattes/migrate)
 Database drivers run migrations. [Add a new database?](database/driver.go)
 
 * [PostgreSQL](database/postgres)
-* [PGX](database/pgx)
+* [PGX v4](database/pgx/v4)
+* [PGX v5](database/pgx/v5)
 * [Redshift](database/redshift)
 * [Ql](database/ql)
 * [Cassandra](database/cassandra)

database/pgx/README.md

@@ -1,39 +1,3 @@
 # pgx
 
-`pgx://user:password@host:port/dbname?query`
-
-| URL Query  | WithInstance Config | Description |
-|------------|---------------------|-------------|
-| `x-migrations-table` | `MigrationsTable` | Name of the migrations table |
-| `x-migrations-table-quoted` | `MigrationsTableQuoted` | By default, migrate quotes the migration table for SQL injection safety reasons. This option disable quoting and naively checks that you have quoted the migration table name. e.g. `"my_schema"."schema_migrations"` |
-| `x-statement-timeout` | `StatementTimeout` | Abort any statement that takes more than the specified number of milliseconds |
-| `x-multi-statement` | `MultiStatementEnabled` | Enable multi-statement execution (default: false) |
-| `x-multi-statement-max-size` | `MultiStatementMaxSize` | Maximum size of single statement in bytes (default: 10MB) |
-| `dbname` | `DatabaseName` | The name of the database to connect to |
-| `search_path` | | This variable specifies the order in which schemas are searched when an object is referenced by a simple name with no schema specified. |
-| `user` | | The user to sign in as |
-| `password` | | The user's password |
-| `host` | | The host to connect to. Values that start with / are for unix domain sockets. (default is localhost) |
-| `port` | | The port to bind to. (default is 5432) |
-| `fallback_application_name` | | An application_name to fall back to if one isn't provided. |
-| `connect_timeout` | | Maximum wait for connection, in seconds. Zero or not specified means wait indefinitely. |
-| `sslcert` | | Cert file location. The file must contain PEM encoded data. |
-| `sslkey` | | Key file location. The file must contain PEM encoded data. |
-| `sslrootcert` | | The location of the root certificate file. The file must contain PEM encoded data. |
-| `sslmode` | | Whether or not to use SSL (disable\|require\|verify-ca\|verify-full) |
-
-
-## Upgrading from v1
-
-1. Write down the current migration version from schema_migrations
-1. `DROP TABLE schema_migrations`
-2. Wrap your existing migrations in transactions ([BEGIN/COMMIT](https://www.postgresql.org/docs/current/static/transaction-iso.html)) if you use multiple statements within one migration.
-3. Download and install the latest migrate version.
-4. Force the current migration version with `migrate force <current_version>`.
-
-## Multi-statement mode
-
-In PostgreSQL running multiple SQL statements in one `Exec` executes them inside a transaction. Sometimes this
-behavior is not desirable because some statements can be only run outside of transaction (e.g.
-`CREATE INDEX CONCURRENTLY`). If you want to use `CREATE INDEX CONCURRENTLY` without activating multi-statement mode
-you have to put such statements in a separate migration files.
+Backends are provided for [pgx v4](v4) and [pgx v5](v5). Links to v4 are exported in this package for backwards compatability.