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Be more careful about marking catalog columns NOT NULL by default.

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The bug fixed in commit 72eab84a5 would not have occurred if initdb
had a less surprising rule about which columns should be marked
NOT NULL by default.  Let's make that rule be strictly that the
column must be fixed-width and its predecessors must be fixed-width
and NOT NULL, removing the hacky and unsafe exceptions for oidvector
and int2vector.

Since we do still want all existing oidvector and int2vector columns
to be marked NOT NULL, we have to put BKI_FORCE_NOT_NULL labels on
them.  But making this less magic and more documented seems like a
good idea, even if it's a shade more verbose.

I didn't bump catversion since the initial catalog contents are
not actually changed by this patch.  Note however that the
contents of postgres.bki do change, and feeding an old copy of
that to a new backend will produce wrong results.

Discussion: https://postgr.es/m/204760.1595181800@sss.pgh.pa.us
This commit is contained in:
Tom Lane
2020-07-21 13:03:48 -04:00
parent 3e66019f15
commit fc032bed2f
9 changed files with 46 additions and 42 deletions
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3
doc/src/sgml/bki.sgml
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@ -119,7 +119,8 @@
require all columns that should be non-nullable to be marked so
in <structname>pg_attribute</structname>. The bootstrap code will
automatically mark catalog columns as <literal>NOT NULL</literal>
if they are fixed-width and are not preceded by any nullable column.
if they are fixed-width and are not preceded by any nullable or
variable-width column.
Where this rule is inadequate, you can force correct marking by using
<literal>BKI_FORCE_NOT_NULL</literal>
and <literal>BKI_FORCE_NULL</literal> annotations as needed.