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docs: Pull renaming and type overrides into separate sections (#2774)
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‎docs/howto/overrides.md‎

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# Overriding types
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The default mapping of PostgreSQL/MySQL types to Go types only uses packages outside
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the standard library when it must.
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For example, the `uuid` PostgreSQL type is mapped to `github.com/google/uuid`.
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If a different Go package for UUIDs is required, specify the package in the
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`overrides` array. In this case, I'm going to use the `github.com/gofrs/uuid`
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instead.
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```yaml
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version: "2"
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sql:
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- schema: "postgresql/schema.sql"
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queries: "postgresql/query.sql"
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engine: "postgresql"
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gen:
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go:
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package: "authors"
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out: "postgresql"
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overrides:
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- db_type: "uuid"
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go_type: "github.com/gofrs/uuid.UUID"
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```
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Each mapping of the `overrides` collection has the following keys:
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- `db_type`:
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- The PostgreSQL or MySQL type to override. Find the full list of supported types in [postgresql_type.go](https://github.com/sqlc-dev/sqlc/blob/main/internal/codegen/golang/postgresql_type.go#L12) or [mysql_type.go](https://github.com/sqlc-dev/sqlc/blob/main/internal/codegen/golang/mysql_type.go#L12). Note that for Postgres you must use the pg_catalog prefixed names where available. Can't be used if the `column` key is defined.
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- `column`:
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- In case the type overriding should be done on specific a column of a table instead of a type. `column` should be of the form `table.column` but you can be even more specific by specifying `schema.table.column` or `catalog.schema.table.column`. Can't be used if the `db_type` key is defined.
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- `go_type`:
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- A fully qualified name to a Go type to use in the generated code.
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- `go_struct_tag`:
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- A reflect-style struct tag to use in the generated code, e.g. `a:"b" x:"y,z"`.
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If you want general json/db tags for all fields, use `emit_db_tags` and/or `emit_json_tags` instead.
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- `nullable`:
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- If `true`, use this type when a column is nullable. Defaults to `false`.
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Note that a single `db_type` override configuration applies to either nullable or non-nullable
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columns, but not both. If you want a single `go_type` to override in both cases, you'll
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need to specify two overrides.
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When generating code, entries using the `column` key will always have preference over
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entries using the `db_type` key in order to generate the struct.
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For more complicated import paths, the `go_type` can also be an object with the following keys:
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- `import`:
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- The import path for the package where the type is defined.
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- `package`:
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- The package name where the type is defined. This should only be necessary when your import path doesn't end with the desired package name.
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- `type`:
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- The type name itself, without any package prefix.
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- `pointer`:
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- If set to `true`, generated code will use pointers to the type rather than the type itself.
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- `slice`:
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- If set to `true`, generated code will use a slice of the type rather than the type itself.
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An example:
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```yaml
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version: "2"
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sql:
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- schema: "postgresql/schema.sql"
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queries: "postgresql/query.sql"
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engine: "postgresql"
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gen:
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go:
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package: "authors"
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out: "postgresql"
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overrides:
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- db_type: "uuid"
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go_type:
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import: "a/b/v2"
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package: "b"
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type: "MyType"
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pointer: true
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```

‎docs/howto/rename.md‎

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# Renaming fields
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Struct field names are generated from column names using a simple algorithm:
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split the column name on underscores and capitalize the first letter of each
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part.
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```
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account -> Account
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spotify_url -> SpotifyUrl
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app_id -> AppID
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```
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If you're not happy with a field's generated name, use the `rename` mapping
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to pick a new name. The keys are column names and the values are the struct
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field name to use.
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```yaml
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version: "2"
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sql:
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- schema: "postgresql/schema.sql"
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queries: "postgresql/query.sql"
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engine: "postgresql"
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gen:
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go:
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package: "authors"
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out: "postgresql"
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rename:
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spotify_url: "SpotifyURL"
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```
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## Tables
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The output structs associated with tables can also be renamed. By default, the struct name will be the singular version of the table name. For example, the `authors` table will generate an `Author` struct.
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```sql
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CREATE TABLE authors (
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id BIGSERIAL PRIMARY KEY,
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name text NOT NULL,
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bio text
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);
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```
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```go
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package db
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import (
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"database/sql"
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)
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type Author struct {
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ID int64
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Name string
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Bio sql.NullString
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}
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```
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To rename this struct, you must use the generated struct name. In this example, that would be `author`. Use the `rename` map to change the name of this struct to `Writer` (note the uppercase `W`).
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```yaml
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version: '1'
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packages:
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- path: db
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engine: postgresql
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schema: query.sql
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queries: query.sql
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rename:
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author: Writer
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```
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```go
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package db
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import (
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"database/sql"
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)
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type Writer struct {
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ID int64
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Name string
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Bio sql.NullString
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}
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```
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## Limitations
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Rename mappings apply to an entire package. Therefore, a column named `foo` and
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a table name `foo` can't be renamed different values.

‎docs/index.rst‎

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howto/ddl.md
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howto/structs.md
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howto/embedding.md
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howto/overrides.md
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howto/rename.md
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howto/vet.md
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howto/managed-databases.md

‎docs/reference/config.md‎

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- `query_parameter_limit`:
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- The number of positional arguments that will be generated for Go functions. To always emit a parameter struct, set this to `0`. Defaults to `1`.
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- `rename`:
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- Customize the name of generated struct fields. Explained in detail on the `Renaming fields` section.
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- Customize the name of generated struct fields. See [Renaming fields](../howto/rename.md) for usage information.
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- `overrides`:
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- It is a collection of definitions that dictates which types are used to map a database types. Explained in detail on the `Type overriding` section.
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- It is a collection of definitions that dictates which types are used to map a database types.
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##### Renaming fields
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##### `overrides`
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Struct field names are generated from column names using a simple algorithm:
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split the column name on underscores and capitalize the first letter of each
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part.
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```
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account -> Account
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spotify_url -> SpotifyUrl
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app_id -> AppID
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```
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If you're not happy with a field's generated name, use the `rename` mapping
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to pick a new name. The keys are column names and the values are the struct
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field name to use.
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```yaml
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version: "2"
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sql:
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- schema: "postgresql/schema.sql"
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queries: "postgresql/query.sql"
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engine: "postgresql"
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gen:
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go:
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package: "authors"
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out: "postgresql"
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rename:
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spotify_url: "SpotifyURL"
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```
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##### Type overriding
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The default mapping of PostgreSQL/MySQL types to Go types only uses packages outside
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the standard library when it must.
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For example, the `uuid` PostgreSQL type is mapped to `github.com/google/uuid`.
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If a different Go package for UUIDs is required, specify the package in the
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`overrides` array. In this case, I'm going to use the `github.com/gofrs/uuid`
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instead.
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```yaml
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version: "2"
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sql:
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- schema: "postgresql/schema.sql"
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queries: "postgresql/query.sql"
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engine: "postgresql"
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gen:
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go:
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package: "authors"
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out: "postgresql"
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overrides:
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- db_type: "uuid"
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go_type: "github.com/gofrs/uuid.UUID"
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```
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Each mapping of the `overrides` collection has the following keys:
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See [Overriding types](../howto/overrides.md) for in-depth guide to using type overrides. Each mapping of the `overrides` collection has the following keys:
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- `db_type`:
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- The PostgreSQL or MySQL type to override. Find the full list of supported types in [postgresql_type.go](https://github.com/sqlc-dev/sqlc/blob/main/internal/codegen/golang/postgresql_type.go#L12) or [mysql_type.go](https://github.com/sqlc-dev/sqlc/blob/main/internal/codegen/golang/mysql_type.go#L12). Note that for Postgres you must use the pg_catalog prefixed names where available. Can't be used if the `column` key is defined.
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- `nullable`:
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- If `true`, use this type when a column is nullable. Defaults to `false`.
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Note that a single `db_type` override configuration applies to either nullable or non-nullable
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columns, but not both. If you want a single `go_type` to override in both cases, you'll
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need to specify two overrides.
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When generating code, entries using the `column` key will always have preference over
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entries using the `db_type` key in order to generate the struct.
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For more complicated import paths, the `go_type` can also be an object with the following keys:
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- `import`:
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- `slice`:
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- If set to `true`, generated code will use a slice of the type rather than the type itself.
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An example:
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```yaml
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version: "2"
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sql:
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- schema: "postgresql/schema.sql"
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queries: "postgresql/query.sql"
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engine: "postgresql"
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gen:
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go:
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package: "authors"
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out: "postgresql"
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overrides:
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- db_type: "uuid"
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go_type:
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import: "a/b/v2"
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package: "b"
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type: "MyType"
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pointer: true
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```
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#### kotlin
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> Removed in v1.17.0 and replaced by the [sqlc-gen-kotlin](https://github.com/sqlc-dev/sqlc-gen-kotlin) plugin. Follow the [migration guide](../guides/migrating-to-sqlc-gen-kotlin) to switch.

‎docs/reference/datatypes.md‎

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Data *dto.BookData
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}
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```
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## Geometry
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### PostGIS
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sqlc can be configured to use the [geom](https://github.com/twpayne/go-geom)
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package for working with PostGIS geometry types.
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```sql
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-- Multipolygons in British National Grid (epsg:27700)
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create table shapes(
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id serial,
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name varchar,
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geom geometry(Multipolygon, 27700)
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);
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-- name: GetShapes :many
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SELECT * FROM shapes;
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```
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```json
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{
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"version": "1",
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"packages": [
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{
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"path": "db",
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"engine": "postgresql",
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"schema": "query.sql",
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"queries": "query.sql"
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}
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],
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"overrides": [
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{
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"db_type": "geometry",
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"go_type": "github.com/twpayne/go-geom.MultiPolygon"
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},
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{
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"db_type": "geometry",
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"go_type": "github.com/twpayne/go-geom.MultiPolygon",
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"null": true
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}
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]
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}
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```

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