get_schema: Get the current schema/catalog of a database-related objects

In SCDB: Easily Access and Maintain Time-Based Versioned Data (Slowly-Changing-Dimension)

Get the current schema/catalog of a database-related objects

Description

Get the current schema/catalog of a database-related objects

Usage

get_catalog(obj, ...)

## S3 method for class ''Microsoft SQL Server''
get_catalog(obj, temporary = FALSE, ...)

get_schema(obj, ...)

## S3 method for class 'PqConnection'
get_schema(obj, temporary = FALSE, ...)

## S3 method for class 'SQLiteConnection'
get_schema(obj, temporary = FALSE, ...)

Arguments

obj	(DBIConnection(1), tbl_dbi(1), Id(1)) The object from which to retrieve a schema/catalog.
...	Further arguments passed to methods.
temporary	(logical(1)) Should the reference be to the temporary schema/catalog?

Value

The catalog is extracted from obj depending on the type of input:

• For ⁠get_catalog.Microsoft SQL Server⁠, the current database context of the connection or "tempdb" if temporary = TRUE.

• For get_schema.tbl_dbi the catalog is determined via id().

• For ⁠get_catalog.\\*⁠, NULL is returned.

The schema is extracted from obj depending on the type of input:

• For get_schema.DBIConnection(), the current schema of the connection if temporary = FALSE. See "Default schema" for more. If temporary = TRUE, the temporary schema of the connection is returned.

• For get_schema.tbl_dbi() the schema is determined via id().

• For get_schema.Id(), the schema is extracted from the Id specification.

Default schema

In some backends, it is possible to modify settings so that when a schema is not explicitly stated in a query, the backend searches for the table in this schema by default. For Postgres databases, this can be shown with ⁠SELECT CURRENT_SCHEMA()⁠ (defaults to public) and modified with ⁠SET search_path TO { schema }⁠.

For SQLite databases, a temp schema for temporary tables always exists as well as a main schema for permanent tables. Additional databases may be attached to the connection with a named schema, but as the attachment must be made after the connection is established, get_schema will never return any of these, as the default schema will always be main.

Examples

  conn <- get_connection()

  dplyr::copy_to(conn, mtcars, name = "mtcars", temporary = FALSE)

  get_schema(conn)
  get_schema(get_table(conn, id("mtcars", conn = conn)))

  get_catalog(conn)
  get_catalog(get_table(conn, id("mtcars", conn = conn)))

  close_connection(conn)

SCDB documentation built on Oct. 4, 2024, 1:09 a.m.