pgsql: Preserve index data in pg_statistic across REINDEX CONCURRENTLY

Preserve index data in pg_statistic across REINDEX CONCURRENTLY

Statistics associated to an index got lost after running REINDEX
CONCURRENTLY, while the non-concurrent case preserves these correctly.
The concurrent and non-concurrent operations need to be consistent for
the end-user, and missing statistics would force to wait for a new
analyze to happen, which could take some time depending on the activity
of the existing autovacuum workers. This issue is fixed by copying any
existing entries in pg_statistic associated to the old index to the new
one. Note that this copy is already done with the data of the index in
the stats collector.

Reported-by: Fabrízio de Royes Mello
Author: Michael Paquier, Fabrízio de Royes Mello
Reviewed-by: Justin Pryzby
Discussion: https://postgr.es/m/CAFcNs+qpFPmiHd1oTXvcPdvAHicJDA9qBUSujgAhUMJyUMb+SA@mail.gmail.com
Backpatch-through: 12

Branch
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REL_13_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/bb62df46bcaa109d5eb1907392034024dde0886e

Modified Files
--------------
src/backend/catalog/heap.c | 41 ++++++++++++++++++++++++++++++
src/backend/catalog/index.c | 3 +++
src/include/catalog/heap.h | 1 +
src/test/regress/expected/create_index.out | 22 ++++++++++++++++
src/test/regress/sql/create_index.sql | 12 +++++++++
5 files changed, 79 insertions(+)