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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-13 13:44:03 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-13 13:44:03 +0000 |
commit | 293913568e6a7a86fd1479e1cff8e2ecb58d6568 (patch) | |
tree | fc3b469a3ec5ab71b36ea97cc7aaddb838423a0c /src/include/common/pg_lzcompress.h | |
parent | Initial commit. (diff) | |
download | postgresql-16-293913568e6a7a86fd1479e1cff8e2ecb58d6568.tar.xz postgresql-16-293913568e6a7a86fd1479e1cff8e2ecb58d6568.zip |
Adding upstream version 16.2.upstream/16.2
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'src/include/common/pg_lzcompress.h')
-rw-r--r-- | src/include/common/pg_lzcompress.h | 93 |
1 files changed, 93 insertions, 0 deletions
diff --git a/src/include/common/pg_lzcompress.h b/src/include/common/pg_lzcompress.h new file mode 100644 index 0000000..2a12b33 --- /dev/null +++ b/src/include/common/pg_lzcompress.h @@ -0,0 +1,93 @@ +/* ---------- + * pg_lzcompress.h - + * + * Definitions for the builtin LZ compressor + * + * src/include/common/pg_lzcompress.h + * ---------- + */ + +#ifndef _PG_LZCOMPRESS_H_ +#define _PG_LZCOMPRESS_H_ + + +/* ---------- + * PGLZ_MAX_OUTPUT - + * + * Macro to compute the buffer size required by pglz_compress(). + * We allow 4 bytes for overrun before detecting compression failure. + * ---------- + */ +#define PGLZ_MAX_OUTPUT(_dlen) ((_dlen) + 4) + + +/* ---------- + * PGLZ_Strategy - + * + * Some values that control the compression algorithm. + * + * min_input_size Minimum input data size to consider compression. + * + * max_input_size Maximum input data size to consider compression. + * + * min_comp_rate Minimum compression rate (0-99%) to require. + * Regardless of min_comp_rate, the output must be + * smaller than the input, else we don't store + * compressed. + * + * first_success_by Abandon compression if we find no compressible + * data within the first this-many bytes. + * + * match_size_good The initial GOOD match size when starting history + * lookup. When looking up the history to find a + * match that could be expressed as a tag, the + * algorithm does not always walk back entirely. + * A good match fast is usually better than the + * best possible one very late. For each iteration + * in the lookup, this value is lowered so the + * longer the lookup takes, the smaller matches + * are considered good. + * + * match_size_drop The percentage by which match_size_good is lowered + * after each history check. Allowed values are + * 0 (no change until end) to 100 (only check + * latest history entry at all). + * ---------- + */ +typedef struct PGLZ_Strategy +{ + int32 min_input_size; + int32 max_input_size; + int32 min_comp_rate; + int32 first_success_by; + int32 match_size_good; + int32 match_size_drop; +} PGLZ_Strategy; + + +/* ---------- + * The standard strategies + * + * PGLZ_strategy_default Recommended default strategy for TOAST. + * + * PGLZ_strategy_always Try to compress inputs of any length. + * Fallback to uncompressed storage only if + * output would be larger than input. + * ---------- + */ +extern PGDLLIMPORT const PGLZ_Strategy *const PGLZ_strategy_default; +extern PGDLLIMPORT const PGLZ_Strategy *const PGLZ_strategy_always; + + +/* ---------- + * Global function declarations + * ---------- + */ +extern int32 pglz_compress(const char *source, int32 slen, char *dest, + const PGLZ_Strategy *strategy); +extern int32 pglz_decompress(const char *source, int32 slen, char *dest, + int32 rawsize, bool check_complete); +extern int32 pglz_maximum_compressed_size(int32 rawsize, + int32 total_compressed_size); + +#endif /* _PG_LZCOMPRESS_H_ */ |