LanguageIndexes

Indexes

index on a column declares an index that starts at it, and index as name names it.

orders.erdOpen in playground
table orders {
  id          bigint    pk
  user_id     bigint    index as idx_orders_user
  status      varchar   index
  created_at  datetime
  index(created_at, status) as idx_orders_time_status
}
The diagram resin draws for orders.erdThe diagram resin draws for orders.erd

Single and composite

index describes an index whose first column is this one. Leave out as when the name is not known. An index over several columns is a table constraint, index(a, b), optionally followed by as name. index(a) over a single column is reported as a warning, with a hint to use the column modifier instead.

An index whose columns are the start of another index's columns adds nothing: index on status next to index(status, created_at) serves no lookup the wider one does not. Lint reports it, and it reports a reference column that no index starts with.

Names

Index and unique names are shown, not checked against a database. A name used twice in one table is an error, though, since it would be ambiguous.

In the diagram

A column with an index carries an IX tag after its name, and composite indexes are listed at the foot of the card. The playground's side panel lists every index of a table, with its name and its columns.

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