pgsql: Fix subscriber invalid memory access on DDL.

Fix subscriber invalid memory access on DDL.

This patch allows building the local relmap cache for a subscribed
relation after processing pending invalidation messages and potential
relcache updates.  Without this, the attributes in the local cache don't
tally with the updated relcache entry leading to invalid memory access.

Reported-by Jehan-Guillaume de Rorthais
Author: Jehan-Guillaume de Rorthais and Vignesh C
Reviewed-by: Amit Kapila
Backpatch-through: 10
Discussion: https://postgr.es/m/20191025175929.7e90dbf5@firost

Branch
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REL_11_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/046830164ee4064623c34930a41c351106338041

Modified Files
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src/backend/replication/logical/relation.c | 38 ++++++++++++++++++++----------
1 file changed, 25 insertions(+), 13 deletions(-)