Fix harmless access to uninitialized memory.
Fix harmless access to uninitialized memory.

When cache invalidations arrive while ri_LoadConstraintInfo() is busy
filling a new cache entry, InvalidateConstraintCacheCallBack() compares
the - not yet initialized - oidHashValue field with the to-be-invalidated
hash value. To fix, check whether the entry is already marked as invalid.

Andres Freund

zeroae/postgres-xl,ovr/postgres-xl,greenplum-db/gpdb,lisakowen/gpdb,50wu/gpdb,xinzweb/gpdb,adam8157/gpdb,ovr/postgres-xl,Postgres-XL/Postgres-XL,jmcatamney/gpdb,ashwinstar/gpdb,jmcatamney/gpdb,lisakowen/gpdb,xinzweb/gpdb,ashwinstar/gpdb,techdragon/Postgres-XL,yazun/postgres-xl,adam8157/gpdb,ovr/postgres-xl,ashwinstar/gpdb,jmcatamney/gpdb,50wu/gpdb,ashwinstar/gpdb,xinzweb/gpdb,yazun/postgres-xl,adam8157/gpdb,adam8157/gpdb,adam8157/gpdb,yazun/postgres-xl,adam8157/gpdb,greenplum-db/gpdb,50wu/gpdb,zeroae/postgres-xl,lisakowen/gpdb,lisakowen/gpdb,50wu/gpdb,oberstet/postgres-xl,lisakowen/gpdb,xinzweb/gpdb,pavanvd/postgres-xl,xinzweb/gpdb,techdragon/Postgres-XL,Postgres-XL/Postgres-XL,jmcatamney/gpdb,oberstet/postgres-xl,yazun/postgres-xl,techdragon/Postgres-XL,greenplum-db/gpdb,jmcatamney/gpdb,oberstet/postgres-xl,yazun/postgres-xl,zeroae/postgres-xl,lisakowen/gpdb,Postgres-XL/Postgres-XL,ashwinstar/gpdb,xinzweb/gpdb,ovr/postgres-xl,jmcatamney/gpdb,ashwinstar/gpdb,zeroae/postgres-xl,greenplum-db/gpdb,pavanvd/postgres-xl,ashwinstar/gpdb,pavanvd/postgres-xl,adam8157/gpdb,adam8157/gpdb,xinzweb/gpdb,greenplum-db/gpdb,pavanvd/postgres-xl,xinzweb/gpdb,ashwinstar/gpdb,techdragon/Postgres-XL,jmcatamney/gpdb,50wu/gpdb,50wu/gpdb,oberstet/postgres-xl,50wu/gpdb,Postgres-XL/Postgres-XL,oberstet/postgres-xl,ovr/postgres-xl,lisakowen/gpdb,zeroae/postgres-xl,50wu/gpdb,greenplum-db/gpdb,greenplum-db/gpdb,jmcatamney/gpdb,techdragon/Postgres-XL,pavanvd/postgres-xl,Postgres-XL/Postgres-XL,greenplum-db/gpdb,lisakowen/gpdb