64 lines
2.2 KiB
C
64 lines
2.2 KiB
C
/*-------------------------------------------------------------------------
|
|
*
|
|
* read_stream.h
|
|
* Mechanism for accessing buffered relation data with look-ahead
|
|
*
|
|
*
|
|
* Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
|
|
* Portions Copyright (c) 1994, Regents of the University of California
|
|
*
|
|
* src/include/storage/read_stream.h
|
|
*
|
|
*-------------------------------------------------------------------------
|
|
*/
|
|
#ifndef READ_STREAM_H
|
|
#define READ_STREAM_H
|
|
|
|
#include "storage/bufmgr.h"
|
|
|
|
/* Default tuning, reasonable for many users. */
|
|
#define READ_STREAM_DEFAULT 0x00
|
|
|
|
/*
|
|
* I/O streams that are performing maintenance work on behalf of potentially
|
|
* many users, and thus should be governed by maintenance_io_concurrency
|
|
* instead of effective_io_concurrency. For example, VACUUM or CREATE INDEX.
|
|
*/
|
|
#define READ_STREAM_MAINTENANCE 0x01
|
|
|
|
/*
|
|
* We usually avoid issuing prefetch advice automatically when sequential
|
|
* access is detected, but this flag explicitly disables it, for cases that
|
|
* might not be correctly detected. Explicit advice is known to perform worse
|
|
* than letting the kernel (at least Linux) detect sequential access.
|
|
*/
|
|
#define READ_STREAM_SEQUENTIAL 0x02
|
|
|
|
/*
|
|
* We usually ramp up from smaller reads to larger ones, to support users who
|
|
* don't know if it's worth reading lots of buffers yet. This flag disables
|
|
* that, declaring ahead of time that we'll be reading all available buffers.
|
|
*/
|
|
#define READ_STREAM_FULL 0x04
|
|
|
|
struct ReadStream;
|
|
typedef struct ReadStream ReadStream;
|
|
|
|
/* Callback that returns the next block number to read. */
|
|
typedef BlockNumber (*ReadStreamBlockNumberCB) (ReadStream *stream,
|
|
void *callback_private_data,
|
|
void *per_buffer_data);
|
|
|
|
extern ReadStream *read_stream_begin_relation(int flags,
|
|
BufferAccessStrategy strategy,
|
|
Relation rel,
|
|
ForkNumber forknum,
|
|
ReadStreamBlockNumberCB callback,
|
|
void *callback_private_data,
|
|
size_t per_buffer_data_size);
|
|
extern Buffer read_stream_next_buffer(ReadStream *stream, void **per_buffer_private);
|
|
extern void read_stream_reset(ReadStream *stream);
|
|
extern void read_stream_end(ReadStream *stream);
|
|
|
|
#endif /* READ_STREAM_H */
|