Обсуждение: pgsql: Create explain_dr.c and move DestReceiver-related code there.

Create explain_dr.c and move DestReceiver-related code there.

explain.c has grown rather large, and the code that deals with the
DestReceiver that supports the SERIALIZE option is pretty easily severable
from the rest of explain.c; hence, move it to a separate file.

Reviewed-by: Peter Geoghegan <pg@bowt.ie>
Discussion: http://postgr.es/m/CA+TgmoYutMw1Jgo8BWUmB3TqnOhsEAJiYO=rOQufF4gPLWmkLQ@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/555960a0fbf0590a744f36e90e69e2501dc06146

Modified Files
--------------
src/backend/commands/Makefile     |   1 +
src/backend/commands/explain.c    | 299 +-----------------------------------
src/backend/commands/explain_dr.c | 308 ++++++++++++++++++++++++++++++++++++++
src/backend/commands/meson.build  |   1 +
src/include/commands/explain_dr.h |  30 ++++
5 files changed, 341 insertions(+), 298 deletions(-)