pgsql: Teach planner how to estimate rows for timestamp generate_series

Teach planner how to estimate rows for timestamp generate_series

This provides the planner with row estimates for
generate_series(TIMESTAMP, TIMESTAMP, INTERVAL),
generate_series(TIMESTAMPTZ, TIMESTAMPTZ, INTERVAL) and
generate_series(TIMESTAMPTZ, TIMESTAMPTZ, INTERVAL, TEXT) when the input
parameter values can be estimated during planning.

Author: David Rowley
Reviewed-by: jian he <jian(dot)universality(at)gmail(dot)com>
Discussion: https://postgr.es/m/CAApHDvrBE%3D%2BASo_sGYmQJ3GvO8GPvX5yxXhRS%3Dt_ybd4odFkhQ%40mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/036bdcec9f9998a6e50711fadce69e482ff18f55

Modified Files
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src/backend/utils/adt/timestamp.c | 88 +++++++++++++++++++++
src/include/catalog/pg_proc.dat | 12 ++-
src/test/regress/expected/misc_functions.out | 110 +++++++++++++++++++++++++++
src/test/regress/sql/misc_functions.sql | 84 ++++++++++++++++++++
4 files changed, 291 insertions(+), 3 deletions(-)