pgsql: Move memory management away from writetup() and tuplesort_put*()

Move memory management away from writetup() and tuplesort_put*()

This commit puts some generic work away from sort-variant-specific function.
In particular, tuplesort_put*() now doesn't need to decrease available memory
and switch to sort context before calling puttuple_common().  writetup()
doesn't need to free SortTuple.tuple and increase available memory.

Discussion: https://postgr.es/m/CAPpHfdvjix0Ahx-H3Jp1M2R%2B_74P-zKnGGygx4OWr%3DbUQ8BNdw%40mail.gmail.com
Author: Alexander Korotkov
Reviewed-by: Pavel Borisov, Maxim Orlov, Matthias van de Meent
Reviewed-by: Andres Freund, John Naylor

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/097366c45f5dfe142eb232dc6d348ca0705a63a9

Modified Files
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src/backend/utils/sort/tuplesort.c | 78 ++++++++++++++++----------------------
1 file changed, 33 insertions(+), 45 deletions(-)