From d3593ff34c83c20c75165624faf6d84803390b36 Mon Sep 17 00:00:00 2001 From: Jeff Davis Date: Fri, 31 Jan 2020 16:43:41 -0800 Subject: [PATCH 1/3] Logical Tape Set: lazily allocate read buffer. The write buffer was already lazily-allocated, so this is more symmetric. It also means that a freshly-rewound tape (whether for reading or writing) is not consuming memory for the buffer. --- src/backend/utils/sort/logtape.c | 27 ++++++++++++++++++++------- 1 file changed, 20 insertions(+), 7 deletions(-) diff --git a/src/backend/utils/sort/logtape.c b/src/backend/utils/sort/logtape.c index 42cfb1f9f98..ba6d6e1f80a 100644 --- a/src/backend/utils/sort/logtape.c +++ b/src/backend/utils/sort/logtape.c @@ -773,15 +773,12 @@ LogicalTapeRewindForRead(LogicalTapeSet *lts, int tapenum, size_t buffer_size) lt->buffer_size = 0; if (lt->firstBlockNumber != -1L) { - lt->buffer = palloc(buffer_size); + /* + * The buffer is lazily allocated in LogicalTapeRead(), but we set the + * size here. + */ lt->buffer_size = buffer_size; } - - /* Read the first block, or reset if tape is empty */ - lt->nextBlockNumber = lt->firstBlockNumber; - lt->pos = 0; - lt->nbytes = 0; - ltsReadFillBuffer(lts, lt); } /* @@ -830,6 +827,22 @@ LogicalTapeRead(LogicalTapeSet *lts, int tapenum, lt = <s->tapes[tapenum]; Assert(!lt->writing); + if (lt->buffer == NULL) + { + /* lazily allocate buffer */ + if (lt->firstBlockNumber != -1L) + { + Assert(lt->buffer_size > 0); + lt->buffer = palloc(lt->buffer_size); + } + + /* Read the first block, or reset if tape is empty */ + lt->nextBlockNumber = lt->firstBlockNumber; + lt->pos = 0; + lt->nbytes = 0; + ltsReadFillBuffer(lts, lt); + } + while (size > 0) { if (lt->pos >= lt->nbytes) -- 2.17.1