Hi,
Since we now allow CHECK constraints to be placed on foreign tables, not
only NOT NULL, I think it'd be better to update docs on considerations
about constraints on foreign tables in fdwhandler.sgml, so as to provide
more general considerations. Please find attached a patch.
Best regards,
Etsuro Fujita
*** a/doc/src/sgml/fdwhandler.sgml
--- b/doc/src/sgml/fdwhandler.sgml
***************
*** 242,254 **** IterateForeignScan (ForeignScanState *node);
<para>
Note that <productname>PostgreSQL</productname>'s executor doesn't care
! whether the rows returned violate any <literal>NOT NULL</literal>
! constraints that were defined on the foreign table columns — but
! the planner does care, and may optimize queries incorrectly if
! <literal>NULL</> values are present in a column declared not to contain
! them. If a <literal>NULL</> value is encountered when the user has
! declared that none should be present, it may be appropriate to raise an
! error (just as you would need to do in the case of a data type mismatch).
</para>
<para>
--- 242,254 ----
<para>
Note that <productname>PostgreSQL</productname>'s executor doesn't care
! whether the rows returned violate any constraints that were defined on
! the foreign table — but the planner does care, and may optimize
! queries incorrectly if there are rows visible in the foreign table that
! do not satisfy a declared constraint. If a constraint is violated when
! the user has declared that the constraint should hold true, it may be
! appropriate to raise an error (just as you would need to do in the case
! of a data type mismatch).
</para>
<para>
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