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https://github.com/timescale/timescaledb.git
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cf009cc584
Hash partitioning previously relied on coercing (casting) values to strings before calculating a hash value, including creating CHECK constraints with casts. This approach is fairly suboptimal from a performance perspective and might have issues related to different character encodings depending on system. Hash partitioning now instead uses a partitioning function that takes an anyelement type that calls type-dependent hash functions internal to PostgreSQL. This should provide more efficient hashing both by avoiding unnecessary string conversions and by using more optimal type-specific hash functions. Support for the previous hash partitioning function is preserved for backwards compatibility. Hypertables created with the previous function will continue to use to old hashing strategy, while new tables will default to the updated hash partitioning. For safety, this change also blocks changing types on hash-partitioned columns, since it seems hard to guarantee the same hash result between different types.
78 lines
2.2 KiB
C
78 lines
2.2 KiB
C
#ifndef TIMESCALEDB_DIMENSION_H
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#define TIMESCALEDB_DIMENSION_H
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#include <postgres.h>
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#include <access/attnum.h>
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#include <access/htup_details.h>
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#include "catalog.h"
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typedef struct PartitioningInfo PartitioningInfo;
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typedef struct DimensionSlice DimensionSlice;
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typedef enum DimensionType
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{
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DIMENSION_TYPE_OPEN,
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DIMENSION_TYPE_CLOSED,
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} DimensionType;
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typedef struct Dimension
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{
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FormData_dimension fd;
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DimensionType type;
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AttrNumber column_attno;
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Oid main_table_relid;
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PartitioningInfo *partitioning;
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} Dimension;
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#define IS_OPEN_DIMENSION(d) \
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((d)->type == DIMENSION_TYPE_OPEN)
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#define IS_CLOSED_DIMENSION(d) \
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((d)->type == DIMENSION_TYPE_CLOSED)
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/*
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* A hyperspace defines how to partition in a N-dimensional space.
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*/
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typedef struct Hyperspace
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{
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int32 hypertable_id;
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Oid main_table_relid;
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uint16 capacity;
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uint16 num_dimensions;
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/* Open dimensions should be stored before closed dimensions */
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Dimension dimensions[FLEXIBLE_ARRAY_MEMBER];
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} Hyperspace;
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#define HYPERSPACE_SIZE(num_dimensions) \
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(sizeof(Hyperspace) + (sizeof(Dimension) * (num_dimensions)))
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/*
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* A point in an N-dimensional hyperspace.
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*/
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typedef struct Point
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{
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int16 cardinality;
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uint8 num_coords;
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/* Open dimension coordinates are stored before the closed coordinates */
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int64 coordinates[FLEXIBLE_ARRAY_MEMBER];
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} Point;
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#define POINT_SIZE(cardinality) \
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(sizeof(Point) + (sizeof(int64) * (cardinality)))
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extern Hyperspace *dimension_scan(int32 hypertable_id, Oid main_table_relid, int16 num_dimension);
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extern DimensionSlice *dimension_calculate_default_slice(Dimension *dim, int64 value);
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extern Point *hyperspace_calculate_point(Hyperspace *h, HeapTuple tuple, TupleDesc tupdesc);
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extern Dimension *hyperspace_get_dimension_by_id(Hyperspace *hs, int32 id);
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extern Dimension *hyperspace_get_dimension(Hyperspace *hs, DimensionType type, Index n);
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extern Dimension *hyperspace_get_dimension_by_name(Hyperspace *hs, DimensionType type, const char *name);
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#define hyperspace_get_open_dimension(space, i) \
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hyperspace_get_dimension(space, DIMENSION_TYPE_OPEN, i)
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#define hyperspace_get_closed_dimension(space, i ) \
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hyperspace_get_dimension(space, DIMENSION_TYPE_CLOSED, i)
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#endif /* TIMESCALEDB_DIMENSION_H */
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