b935eb7da3
While at it also update the comments in walmethods.h to make it less likely for mistakes like this to appear in the future (thanks to Tom for improvements to the comments). And finally, in passing change the return type of walmethod.getlasterror to being const, also per suggestion from Tom.
95 lines
3.0 KiB
C
95 lines
3.0 KiB
C
/*-------------------------------------------------------------------------
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*
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* walmethods.h
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*
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* Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
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*
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* IDENTIFICATION
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* src/bin/pg_basebackup/walmethods.h
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*-------------------------------------------------------------------------
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*/
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typedef void *Walfile;
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typedef enum
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{
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CLOSE_NORMAL,
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CLOSE_UNLINK,
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CLOSE_NO_RENAME
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} WalCloseMethod;
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/*
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* A WalWriteMethod structure represents the different methods used
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* to write the streaming WAL as it's received.
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*
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* All methods that have a failure return indicator will set state
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* allowing the getlasterror() method to return a suitable message.
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* Commonly, errno is this state (or part of it); so callers must take
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* care not to clobber errno between a failed method call and use of
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* getlasterror() to retrieve the message.
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*/
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typedef struct WalWriteMethod WalWriteMethod;
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struct WalWriteMethod
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{
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/*
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* Open a target file. Returns Walfile, or NULL if open failed. If a temp
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* suffix is specified, a file with that name will be opened, and then
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* automatically renamed in close(). If pad_to_size is specified, the file
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* will be padded with NUL up to that size, if supported by the Walmethod.
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*/
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Walfile(*open_for_write) (const char *pathname, const char *temp_suffix, size_t pad_to_size);
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/*
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* Close an open Walfile, using one or more methods for handling automatic
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* unlinking etc. Returns 0 on success, other values for error.
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*/
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int (*close) (Walfile f, WalCloseMethod method);
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/* Check if a file exist */
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bool (*existsfile) (const char *pathname);
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/* Return the size of a file, or -1 on failure. */
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ssize_t (*get_file_size) (const char *pathname);
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/*
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* Write count number of bytes to the file, and return the number of bytes
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* actually written or -1 for error.
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*/
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ssize_t (*write) (Walfile f, const void *buf, size_t count);
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/* Return the current position in a file or -1 on error */
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off_t (*get_current_pos) (Walfile f);
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/*
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* fsync the contents of the specified file. Returns 0 on success.
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*/
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int (*sync) (Walfile f);
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/*
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* Clean up the Walmethod, closing any shared resources. For methods like
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* tar, this includes writing updated headers. Returns true if the
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* close/write/sync of shared resources succeeded, otherwise returns false
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* (but the resources are still closed).
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*/
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bool (*finish) (void);
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/* Return a text for the last error in this Walfile */
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const char *(*getlasterror) (void);
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};
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/*
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* Available WAL methods:
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* - WalDirectoryMethod - write WAL to regular files in a standard pg_xlog
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* - TarDirectoryMethod - write WAL to a tarfile corresponding to pg_xlog
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* (only implements the methods required for pg_basebackup,
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* not all those required for pg_receivewal)
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*/
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WalWriteMethod *CreateWalDirectoryMethod(const char *basedir,
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int compression, bool sync);
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WalWriteMethod *CreateWalTarMethod(const char *tarbase, int compression, bool sync);
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/* Cleanup routines for previously-created methods */
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void FreeWalDirectoryMethod(void);
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void FreeWalTarMethod(void);
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