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/*-------------------------------------------------------------------------
*
* toast_compression.h
* Functions for toast compression.
*
* Copyright (c) 2021, PostgreSQL Global Development Group
*
* src/include/access/toast_compression.h
*
*-------------------------------------------------------------------------
*/
#ifndef TOAST_COMPRESSION_H
#define TOAST_COMPRESSION_H
#include "utils/guc.h"
/* GUCs */
extern char *default_toast_compression;
/* default compression method if not specified. */
#define DEFAULT_TOAST_COMPRESSION "pglz"
/*
* Built-in compression method-id. The toast compression header will store
* this in the first 2 bits of the raw length. These built-in compression
* method-id are directly mapped to the built-in compression methods.
*/
typedef enum ToastCompressionId
{
TOAST_PGLZ_COMPRESSION_ID = 0,
TOAST_LZ4_COMPRESSION_ID = 1,
TOAST_INVALID_COMPRESSION_ID = 2
} ToastCompressionId;
/*
* Built-in compression methods. pg_attribute will store this in the
* attcompression column.
*/
#define TOAST_PGLZ_COMPRESSION 'p'
#define TOAST_LZ4_COMPRESSION 'l'
#define InvalidCompressionMethod '\0'
#define CompressionMethodIsValid(cm) ((bool) ((cm) != InvalidCompressionMethod))
#define NO_LZ4_SUPPORT() \
ereport(ERROR, \
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED), \
errmsg("unsupported LZ4 compression method"), \
errdetail("This functionality requires the server to be built with lz4 support."), \
errhint("You need to rebuild PostgreSQL using --with-lz4.")))
#define IsStorageCompressible(storage) ((storage) != TYPSTORAGE_PLAIN && \
(storage) != TYPSTORAGE_EXTERNAL)
/*
* GetCompressionMethodName - Get compression method name
*/
static inline const char *
GetCompressionMethodName(char method)
{
switch (method)
{
case TOAST_PGLZ_COMPRESSION:
return "pglz";
case TOAST_LZ4_COMPRESSION:
return "lz4";
default:
elog(ERROR, "invalid compression method %c", method);
return NULL; /* keep compiler quiet */
}
}
/*
* CompressionNameToMethod - Get compression method from compression name
*
* Search in the available built-in methods. If the compression not found
* in the built-in methods then return InvalidCompressionMethod.
*/
static inline char
CompressionNameToMethod(char *compression)
{
if (strcmp(compression, "pglz") == 0)
return TOAST_PGLZ_COMPRESSION;
else if (strcmp(compression, "lz4") == 0)
{
#ifndef USE_LZ4
NO_LZ4_SUPPORT();
#endif
return TOAST_LZ4_COMPRESSION;
}
return InvalidCompressionMethod;
}
/*
* GetDefaultToastCompression -- get the default toast compression method
*
* This exists to hide the use of the default_toast_compression GUC variable.
*/
static inline char
GetDefaultToastCompression(void)
{
return CompressionNameToMethod(default_toast_compression);
}
/* pglz compression/decompression routines */
extern struct varlena *pglz_compress_datum(const struct varlena *value);
extern struct varlena *pglz_decompress_datum(const struct varlena *value);
extern struct varlena *pglz_decompress_datum_slice(const struct varlena *value,
int32 slicelength);
/* lz4 compression/decompression routines */
extern struct varlena *lz4_compress_datum(const struct varlena *value);
extern struct varlena *lz4_decompress_datum(const struct varlena *value);
extern struct varlena *lz4_decompress_datum_slice(const struct varlena *value,
int32 slicelength);
extern ToastCompressionId toast_get_compression_id(struct varlena *attr);
extern bool check_default_toast_compression(char **newval, void **extra,
GucSource source);
#endif /* TOAST_COMPRESSION_H */
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