Documentation Source Text

  Examples:
}
CODE {
  SELECT MIN(x) FROM table;
  SELECT MAX(x)+1 FROM table;
}

HEADING 1 {Automatic Indexes} autoindex {automatic indexing} {Automatic indexing}

PARAGRAPH {
  ^(When no indices are available to aid the evaluation of a query, SQLite
  might create an automatic index that lasts only for the duration
  of a single SQL statement.)^
  Since the cost of constructing the automatic index is
  O(NlogN) (where N is the number of entries in the table) and the cost of

  the [automatic_index pragma].  Automatic indexing is turned on by
  default, but this can be changed so that automatic indexing is off
  by default using the [SQLITE_DEFAULT_AUTOMATIC_INDEX] compile-time option.
  The ability to create automatic indices can be completely disabled by
  compiling with the [SQLITE_OMIT_AUTOMATIC_INDEX] compile-time option.
}
PARAGRAPH {
  In SQLite version 3.8.0 and later, 
  an [SQLITE_WARNING_AUTOINDEX] message is sent
  to the [error log] every time a statement is prepared that uses an
  automatic index.  Application developers can and should use these warnings
  to identify the need for new persistent indices in the schema.
}
PARAGRAPH {
  Do not confuse automatic indexes with the [internal indexes] (having names
  like "sqlite_autoindex_<i>table</i>_<i>N</i>") that are sometimes
  created to implement a [PRIMARY KEY constraint] or [UNIQUE constraint].
  The automatic indexes described here exist only for the duration of a
  single query, are never persisted to disk, and are only visible to a
  single database connection.  Internal indexes are part of the implementation
  of PRIMARY KEY and UNIQUE constraints, are long-lasting and persisted
  to disk, and are visible to all database connections.  The term "autoindex"
  appears in the names of [internal indexes] for legacy reasons and does
  not indicate that internal indexes and automatic indexes are related.
}  

</tcl>