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b813d143ae
so that precision of result is always at least as good as you'd get from float8 arithmetic (ie, always at least 16 digits of accuracy). Per pg_hackers discussion a few days ago.
91 lines
2.6 KiB
C
91 lines
2.6 KiB
C
/* ----------
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* numeric.h
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*
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* Definitions for the exact numeric data type of Postgres
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*
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* 1998 Jan Wieck
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*
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* $Id: numeric.h,v 1.16 2002/10/02 19:21:26 tgl Exp $
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*
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* ----------
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*/
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#ifndef _PG_NUMERIC_H_
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#define _PG_NUMERIC_H_
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/*
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* Hardcoded precision limit - arbitrary, but must be small enough that
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* dscale values will fit in 14 bits.
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*/
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#define NUMERIC_MAX_PRECISION 1000
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/*
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* Internal limits on the scales chosen for calculation results
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*/
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#define NUMERIC_MAX_DISPLAY_SCALE NUMERIC_MAX_PRECISION
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#define NUMERIC_MIN_DISPLAY_SCALE 0
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#define NUMERIC_MAX_RESULT_SCALE (NUMERIC_MAX_PRECISION * 2)
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/*
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* For inherently inexact calculations such as division and square root,
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* we try to get at least this many significant digits; the idea is to
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* deliver a result no worse than float8 would.
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*/
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#define NUMERIC_MIN_SIG_DIGITS 16
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/*
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* Standard number of extra digits carried internally while doing
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* inexact calculations.
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*/
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#define NUMERIC_EXTRA_DIGITS 4
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/*
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* Sign values and macros to deal with packing/unpacking n_sign_dscale
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*/
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#define NUMERIC_SIGN_MASK 0xC000
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#define NUMERIC_POS 0x0000
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#define NUMERIC_NEG 0x4000
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#define NUMERIC_NAN 0xC000
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#define NUMERIC_DSCALE_MASK 0x3FFF
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#define NUMERIC_SIGN(n) ((n)->n_sign_dscale & NUMERIC_SIGN_MASK)
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#define NUMERIC_DSCALE(n) ((n)->n_sign_dscale & NUMERIC_DSCALE_MASK)
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#define NUMERIC_IS_NAN(n) (NUMERIC_SIGN(n) != NUMERIC_POS && \
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NUMERIC_SIGN(n) != NUMERIC_NEG)
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/*
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* The Numeric data type stored in the database
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*
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* NOTE: by convention, values in the packed form have been stripped of
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* all leading and trailing zeroes (except there will be a trailing zero
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* in the last byte, if the number of digits is odd). In particular,
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* if the value is zero, there will be no digits at all! The weight is
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* arbitrary in that case, but we normally set it to zero.
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*/
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typedef struct NumericData
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{
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int32 varlen; /* Variable size */
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int16 n_weight; /* Weight of 1st digit */
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uint16 n_rscale; /* Result scale */
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uint16 n_sign_dscale; /* Sign + display scale */
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unsigned char n_data[1]; /* Digit data (2 decimal digits/byte) */
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} NumericData;
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typedef NumericData *Numeric;
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#define NUMERIC_HDRSZ (sizeof(int32) + sizeof(uint16) * 3)
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/*
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* fmgr interface macros
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*/
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#define DatumGetNumeric(X) ((Numeric) PG_DETOAST_DATUM(X))
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#define DatumGetNumericCopy(X) ((Numeric) PG_DETOAST_DATUM_COPY(X))
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#define NumericGetDatum(X) PointerGetDatum(X)
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#define PG_GETARG_NUMERIC(n) DatumGetNumeric(PG_GETARG_DATUM(n))
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#define PG_GETARG_NUMERIC_COPY(n) DatumGetNumericCopy(PG_GETARG_DATUM(n))
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#define PG_RETURN_NUMERIC(x) return NumericGetDatum(x)
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#endif /* _PG_NUMERIC_H_ */
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