Adding CHECK to NODES?

philip_at_apache.org writes:

> Author: philip
> Date: Fri Mar 1 10:02:20 2013
> New Revision: 1451549
>
> URL: http://svn.apache.org/r1451549
> Log:
> Store NULL rather than 0 when not setting NODES.moved_here TRUE.
>
> * subversion/libsvn_wc/wc_db.c
> (insert_working_node, db_op_copy_shadowed_layer): Only bind
> moved_here if set.

NODES.moved_here is an SQLite INTEGER used as a boolean. Most of the
code uses 1 to indicate moved here and NULL to indicate not moved here.
There were a few places that were setting moved_here to 0, I have now
removed those.

I tracked down the places that need to be changed by temporarily adding:

  CHECK (moved_here IS NULL OR moved_here = 1)

to the NODES table definition in wc-metadata.sql. I imagine there is a
cost associated which such a check but it is probably small. Should we
add checks like this permanently? Should we attempt to benchmark the
cost? I guess the cost is only on INSERT/REPLACE/UPDATE and not on
SELECT? Are there other columns that should have CHECKs?

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