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/*-------------------------------------------------------------------------
*
* rewind_source.h
* Abstraction for fetching from source server.
*
* The source server can be either a libpq connection to a live system,
* or a local data directory. The 'rewind_source' struct abstracts the
* operations to fetch data from the source system, so that the rest of
* the code doesn't need to care what kind of a source its dealing with.
*
* Copyright (c) 2013-2023, PostgreSQL Global Development Group
*
*-------------------------------------------------------------------------
*/
#ifndef REWIND_SOURCE_H
#define REWIND_SOURCE_H
#include "access/xlogdefs.h"
#include "file_ops.h"
#include "filemap.h"
#include "libpq-fe.h"
typedef struct rewind_source
{
/*
* Traverse all files in the source data directory, and call 'callback' on
* each file.
*/
void (*traverse_files) (struct rewind_source *,
process_file_callback_t callback);
/*
* Fetch a single file into a malloc'd buffer. The file size is returned
* in *filesize. The returned buffer is always zero-terminated, which is
* handy for text files.
*/
char *(*fetch_file) (struct rewind_source *, const char *path,
size_t *filesize);
/*
* Request to fetch (part of) a file in the source system, specified by an
* offset and length, and write it to the same offset in the corresponding
* target file. The source implementation may queue up the request and
* execute it later when convenient. Call finish_fetch() to flush the
* queue and execute all requests.
*/
void (*queue_fetch_range) (struct rewind_source *, const char *path,
off_t offset, size_t len);
/*
* Like queue_fetch_range(), but requests replacing the whole local file
* from the source system. 'len' is the expected length of the file,
* although when the source is a live server, the file may change
* concurrently. The implementation is not obliged to copy more than 'len'
* bytes, even if the file is larger. However, to avoid copying a
* truncated version of the file, which can cause trouble if e.g. a
* configuration file is modified concurrently, the implementation should
* try to copy the whole file, even if it's larger than expected.
*/
void (*queue_fetch_file) (struct rewind_source *, const char *path,
size_t len);
/*
* Execute all requests queued up with queue_fetch_range().
*/
void (*finish_fetch) (struct rewind_source *);
/*
* Get the current WAL insert position in the source system.
*/
XLogRecPtr (*get_current_wal_insert_lsn) (struct rewind_source *);
/*
* Free this rewind_source object.
*/
void (*destroy) (struct rewind_source *);
} rewind_source;
/* in libpq_source.c */
extern rewind_source *init_libpq_source(PGconn *conn);
/* in local_source.c */
extern rewind_source *init_local_source(const char *datadir);
#endif /* REWIND_SOURCE_H */
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