pgsql: Ensure relcache consistency around generated columns

Ensure relcache consistency around generated columns

In certain transient states, it's possible that a table has attributes
with attgenerated set but no default expressions in pg_attrdef yet.
In that case, the old code path would not set
relation->rd_att->constr->has_generated_stored, unless
relation->rd_att->constr was also populated for some other reason.
There was probably no practical impact, but it's better to keep this
consistent.

Reported-by: Andres Freund <andres(at)anarazel(dot)de>
Discussion: https://www.postgresql.org/message-id/flat/20200115181105.ad6ab6dlgyww3lb6%40alap3.anarazel.de

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/fc7a5e9eaa2fa34b053ffe52e0e57f1fd6b1f939

Modified Files
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src/backend/utils/cache/relcache.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)