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Create normalised database schemas from functional dependencies

Source: R/normalise.r
normalise.Rd

Creates a database schema from given functional dependencies, satisfying at least third normal form, using Bernstein's synthesis.

Usage

normalise(
  dependencies,
  single_ref = FALSE,
  ensure_lossless = TRUE,
  reduce_attributes = TRUE,
  remove_avoidable = FALSE,
  constants_name = "constants",
  progress = FALSE,
  progress_file = ""
)

Arguments

dependencies

a functional_dependency object, as given by discover.

single_ref

a logical, FALSE by default. If TRUE, then only one reference between each relation pair is kept when generating foreign key references. If a pair has multiple references, the kept reference refers to the earliest key for the child relation, as sorted by priority order.

ensure_lossless

a logical, TRUE by default. If TRUE, and the decomposition isn't lossless, an extra relation is added to make the decomposition lossless.

reduce_attributes

a logical, TRUE by default. If TRUE, dependencies are checked for determinant attributes that are made redundant by the other dependencies. This is redundant if dependencies is output from discover, since there will be no such redundant attributes.

remove_avoidable

a logical, indicating whether to remove avoidable attributes in relations. If so, then an attribute are removed from relations if the keys can be changed such that it is not needed to preserve the given functional dependencies.

constants_name

a scalar character, giving the name for any relation created to store constant attributes. If this is the same as a generated relation name, it will be changed, with a warning, to ensure that all relations have a unique name.

progress

a logical, for whether to display progress to the user during dependency search in discover.

progress_file

a scalar character or a connection. If progress is non-zero, determines where the progress is written to, in the same way as the file argument for cat.

Value

A database_schema object, containing the synthesis relation schemas and the created foreign key references.

Details

This is a wrapper function for applying synthesise and autoref, in order. For creating relation schemas and foreign key references separately, use these functions directly. See both functions for examples.

For details on the synthesis algorithm used, see synthesise.