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Use streaming I/O in pg_prewarm.

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Instead of calling ReadBuffer() repeatedly, use the new streaming
interface.  This commit provides a very simple example of such a
transformation.

Discussion: https://postgr.es/m/CA+hUKGJkOiOCa+mag4BF+zHo7qo=o9CFheB8=g6uT5TUm2gkvA@mail.gmail.com
This commit is contained in:
Thomas Munro 2024-04-03 00:57:17 +13:00
parent b5a9b18cd0
commit 3a352df05e
1 changed files with 39 additions and 1 deletions
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40
contrib/pg_prewarm/pg_prewarm.c
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@ -19,6 +19,7 @@
#include "fmgr.h"
#include "miscadmin.h"
#include "storage/bufmgr.h"
#include "storage/read_stream.h"
#include "storage/smgr.h"
#include "utils/acl.h"
#include "utils/builtins.h"
@ -38,6 +39,25 @@ typedef enum
static PGIOAlignedBlock blockbuffer;
struct pg_prewarm_read_stream_private
{
BlockNumber blocknum;
int64 last_block;
};
static BlockNumber
pg_prewarm_read_stream_next_block(ReadStream *stream,
void *callback_private_data,
void *per_buffer_data)
{
struct pg_prewarm_read_stream_private *p = callback_private_data;
if (p->blocknum <= p->last_block)
return p->blocknum++;
return InvalidBlockNumber;
}
/*
* pg_prewarm(regclass, mode text, fork text,
* first_block int8, last_block int8)
@ -183,18 +203,36 @@ pg_prewarm(PG_FUNCTION_ARGS)
}
else if (ptype == PREWARM_BUFFER)
{
struct pg_prewarm_read_stream_private p;
ReadStream *stream;
/*
* In buffer mode, we actually pull the data into shared_buffers.
*/
/* Set up the private state for our streaming buffer read callback. */
p.blocknum = first_block;
p.last_block = last_block;
stream = read_stream_begin_relation(READ_STREAM_FULL,
NULL,
rel,
forkNumber,
pg_prewarm_read_stream_next_block,
&p,
0);
for (block = first_block; block <= last_block; ++block)
{
Buffer buf;
CHECK_FOR_INTERRUPTS();
buf = ReadBufferExtended(rel, forkNumber, block, RBM_NORMAL, NULL);
buf = read_stream_next_buffer(stream, NULL);
ReleaseBuffer(buf);
++blocks_done;
}
Assert(read_stream_next_buffer(stream, NULL) == InvalidBuffer);
read_stream_end(stream);
}
/* Close relation, release lock. */