Обсуждение: pgsql: Consider cheap startup paths in add_paths_to_append_rel

Consider cheap startup paths in add_paths_to_append_rel

6b94e7a6d did this for ordered append paths to allow fast startup
MergeAppends, however, nothing was done for the Append case.

Here we adjust add_paths_to_append_rel() to have it build an AppendPath
containing the cheapest startup paths from each of the child relations
when the append rel has "consider_startup" set.

Author: Andy Fan, David Rowley
Discussion: https://www.postgresql.org/message-id/CAKU4AWrXSkUV=Pt-gRxQT7EbfUeNssprGyNsB=5mJibFZ6S3ww@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/a8a968a8212ee3ef7f22795c834b33d871fac262

Modified Files
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src/backend/optimizer/path/allpaths.c | 21 +++++++++++++++++++++
src/test/regress/expected/union.out   | 21 +++++++++++++++++++++
src/test/regress/sql/union.sql        | 11 +++++++++++
3 files changed, 53 insertions(+)