Replace polyphase merge algorithm with a simple balanced k-way merge.

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The advantage of polyphase merge is that it can reuse the input tapes as
output tapes efficiently, but that is irrelevant on modern hardware, when
we can easily emulate any number of tape drives. The number of input tapes
we can/should use during merging is limited by work_mem, but output tapes
that we are not currently writing to only cost a little bit of memory, so
there is no need to skimp on them.

This makes sorts that need multiple merge passes faster.

Discussion: https://www.postgresql.org/message-id/420a0ec7-602c-d406-1e75-1ef7ddc58d83%40iki.fi
Reviewed-by: Peter Geoghegan, Zhihong Yu, John Naylor

pull/73/head

Heikki Linnakangas 4 years ago

parent c4649cce39

commit 65014000b3

1 changed files with 293 additions and 369 deletions

Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL

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1. 662
     src/backend/utils/sort/tuplesort.c

662

src/backend/utils/sort/tuplesort.c

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