Commit 653e1972 authored by Tim Peters's avatar Tim Peters

Added new "BTree Diagnostic Tools" subsubsection, pointing to the

BTrees.check module and to the BTree._check() method.
parent 91fa5293
......@@ -359,3 +359,25 @@ only with great care:
or implicitly) on an address-based comparison result will
eventually cause serious failure.
\end{enumerate}
\subsubsection{BTree Diagnostic Tools}
A BTree (or TreeSet) is a complex data structure, really a graph of
variable-size nodes, connected in multiple ways via three distinct kinds
of C pointers. There are some tools available to help check internal
consistency of a BTree as a whole.
Most generally useful is the \module{BTrees.check} module. The
\function{check.check()} function examines a BTree (or Bucket, Set, or
TreeSet) for value-based consistency, such as that the keys are in
strictly increasing order. See the function docstring for details.
The \function{check.display()} function displays the internal structure
of a BTree.
BTrees and TreeSets also have a \method{_check()} method. This verifies
that the (possibly many) internal pointers in a BTree or TreeSet
are mutually consistent, and raises \exception{AssertionError} if they're
not. If a \method{_check()} method call fails, in may point to a bug
in the implementation of BTrees or conflict resolution, or may point to
database corruption.
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