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6832ed2ca5
This PR modifies the toast type for compressed columns based on the algorithm used for compression.
147 lines
5.2 KiB
C
147 lines
5.2 KiB
C
/*
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* This file and its contents are licensed under the Timescale License.
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* Please see the included NOTICE for copyright information and
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* LICENSE-TIMESCALE for a copy of the license.
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*/
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#ifndef TIMESCALEDB_TSL_COMPRESSION_COMPRESSION_H
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#define TIMESCALEDB_TSL_COMPRESSION_COMPRESSION_H
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#include <postgres.h>
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#include <c.h>
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#include <fmgr.h>
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#include <lib/stringinfo.h>
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/*
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* Compressed data starts with a specialized varlen type starting with the usual
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* varlen header, and followed by a version specifying which compression
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* algorithm was used. This allows us to share the same code across different
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* SQL datatypes. Currently we only allow 127 versions, as we may want to use
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* variable-width integer type in the event we have more than a non-trivial
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* number of compression algorithms.
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*/
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#define CompressedDataHeaderFields \
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char vl_len_[4]; \
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uint8 compression_algorithm
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typedef struct CompressedDataHeader
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{
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CompressedDataHeaderFields;
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} CompressedDataHeader;
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/* On 32-bit architectures, 64-bit values are boxed when returned as datums. To avoid
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this overhead we have this type and corresponding iterators for efficiency. The iterators
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are private to the compression algorithms for now. */
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typedef uint64 DecompressDataInternal;
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typedef struct DecompressResultInternal
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{
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DecompressDataInternal val;
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bool is_null;
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bool is_done;
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} DecompressResultInternal;
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/* This type returns datums and is used as our main interface */
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typedef struct DecompressResult
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{
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Datum val;
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bool is_null;
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bool is_done;
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} DecompressResult;
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/* Forward declaration of ColumnCompressionInfo so we don't need to include catalog.h */
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typedef struct FormData_hypertable_compression ColumnCompressionInfo;
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typedef struct Compressor Compressor;
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struct Compressor
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{
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void (*append_null)(Compressor *compressord);
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void (*append_val)(Compressor *compressor, Datum val);
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void *(*finish)(Compressor *data);
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};
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typedef struct DecompressionIterator
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{
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uint8 compression_algorithm;
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bool forward;
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Oid element_type;
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DecompressResult (*try_next)(struct DecompressionIterator *);
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} DecompressionIterator;
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/*
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* TOAST_STORAGE_EXTENDED for out of line storage.
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* TOAST_STORAGE_EXTERNAL for out of line storage + native PG toast compression
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* used when you want to enable postgres native toast
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* compression on the output of the compression algorithm.
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*/
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typedef enum
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{
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TOAST_STORAGE_EXTERNAL,
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TOAST_STORAGE_EXTENDED
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} CompressionStorage;
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typedef struct CompressionAlgorithmDefinition
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{
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DecompressionIterator *(*iterator_init_forward)(Datum, Oid element_type);
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DecompressionIterator *(*iterator_init_reverse)(Datum, Oid element_type);
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void (*compressed_data_send)(CompressedDataHeader *, StringInfo);
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Datum (*compressed_data_recv)(StringInfo);
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Compressor *(*compressor_for_type)(Oid element_type);
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CompressionStorage compressed_data_storage;
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} CompressionAlgorithmDefinition;
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typedef enum CompressionAlgorithms
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{
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/* Not a real algorithm, if this does get used, it's a bug in the code */
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_INVALID_COMPRESSION_ALGORITHM = 0,
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COMPRESSION_ALGORITHM_ARRAY,
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COMPRESSION_ALGORITHM_DICTIONARY,
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COMPRESSION_ALGORITHM_GORILLA,
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COMPRESSION_ALGORITHM_DELTADELTA,
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/* When adding an algorithm also add a static assert statement below */
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/* end of real values */
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_END_COMPRESSION_ALGORITHMS,
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_MAX_NUM_COMPRESSION_ALGORITHMS = 128,
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} CompressionAlgorithms;
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extern Datum tsl_compressed_data_decompress_forward(PG_FUNCTION_ARGS);
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extern Datum tsl_compressed_data_decompress_reverse(PG_FUNCTION_ARGS);
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extern Datum tsl_compressed_data_send(PG_FUNCTION_ARGS);
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extern Datum tsl_compressed_data_recv(PG_FUNCTION_ARGS);
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extern Datum tsl_compressed_data_in(PG_FUNCTION_ARGS);
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extern Datum tsl_compressed_data_out(PG_FUNCTION_ARGS);
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static void
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pg_attribute_unused() assert_num_compression_algorithms_sane(void)
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{
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/* make sure not too many compression algorithms */
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StaticAssertStmt(_END_COMPRESSION_ALGORITHMS <= _MAX_NUM_COMPRESSION_ALGORITHMS,
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"Too many compression algorthims, make sure a decision on variable-length "
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"version field has been made.");
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/* existing indexes that MUST NEVER CHANGE */
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StaticAssertStmt(COMPRESSION_ALGORITHM_ARRAY == 1, "algorithm index has changed");
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StaticAssertStmt(COMPRESSION_ALGORITHM_DICTIONARY == 2, "algorithm index has changed");
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StaticAssertStmt(COMPRESSION_ALGORITHM_GORILLA == 3, "algorithm index has changed");
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StaticAssertStmt(COMPRESSION_ALGORITHM_DELTADELTA == 4, "algorithm index has changed");
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/* This should change when adding a new algorithm after adding the new algorithm to the assert
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* list above. This statement prevents adding a new algorithm without updating the asserts above
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*/
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StaticAssertStmt(_END_COMPRESSION_ALGORITHMS == 5,
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"number of algorithms have changed, the asserts should be updated");
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}
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extern CompressionStorage compression_get_toast_storage(CompressionAlgorithms algo);
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extern void compress_chunk(Oid in_table, Oid out_table,
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const ColumnCompressionInfo **column_compression_info, int num_columns);
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extern void decompress_chunk(Oid in_table, Oid out_table);
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extern DecompressionIterator *(*tsl_get_decompression_iterator_init(
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CompressionAlgorithms algorithm, bool reverse))(Datum, Oid element_type);
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#endif
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