Allow numeric to use a more compact, 2-byte header in many cases.
Review by Brendan Jurd and Tom Lane.
This commit is contained in:
Robert Haas
parent
db04f2b322
commit
145343534c
@ -14,7 +14,7 @@
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* Copyright (c) 1998-2010, PostgreSQL Global Development Group
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/utils/adt/numeric.c,v 1.124 2010/07/30 04:30:23 rhaas Exp $
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* $PostgreSQL: pgsql/src/backend/utils/adt/numeric.c,v 1.125 2010/08/03 23:09:29 rhaas Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -35,38 +35,6 @@
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#include "utils/int8.h"
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#include "utils/numeric.h"
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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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#define NUMERIC_HDRSZ (VARHDRSZ + sizeof(uint16) + sizeof(int16))
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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 zero digits (where a "digit" is of base NBASE).
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* In particular, if the value is zero, there will be no digits at all!
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* The weight is arbitrary in that case, but we normally set it to zero.
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*/
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struct NumericData
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{
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int32 vl_len_; /* varlena header (do not touch directly!) */
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uint16 n_sign_dscale; /* Sign + display scale */
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int16 n_weight; /* Weight of 1st digit */
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char n_data[1]; /* Digits (really array of NumericDigit) */
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};
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/* ----------
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* Uncomment the following to enable compilation of dump_numeric()
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* and dump_var() and to get a dump of any result produced by make_result().
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@ -120,6 +88,122 @@ typedef signed char NumericDigit;
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typedef int16 NumericDigit;
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#endif
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/*
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* The Numeric type as stored on disk.
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*
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* If the high bits of the first word of a NumericChoice (n_header, or
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* n_short.n_header, or n_long.n_sign_dscale) are NUMERIC_SHORT, then the
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* numeric follows the NumericShort format; if they are NUMERIC_POS or
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* NUMERIC_NEG, it follows the NumericLong format. If they are NUMERIC_NAN,
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* it is a NaN. We currently always store a NaN using just two bytes (i.e.
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* only n_header), but previous releases used only the NumericLong format,
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* so we might find 4-byte NaNs on disk if a database has been migrated using
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* pg_upgrade. In either case, when the high bits indicate a NaN, the
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* remaining bits are never examined. Currently, we always initialize these
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* to zero, but it might be possible to use them for some other purpose in
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* the future.
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*
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* In the NumericShort format, the remaining 14 bits of the header word
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* (n_short.n_header) are allocated as follows: 1 for sign (positive or
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* negative), 6 for dynamic scale, and 7 for weight. In practice, most
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* commonly-encountered values can be represented this way.
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*
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* In the NumericLong format, the remaining 14 bits of the header word
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* (n_long.n_sign_dscale) represent the display scale; and the weight is
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* stored separately in n_weight.
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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 zero digits (where a "digit" is of base NBASE).
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* In particular, if the value is zero, there will be no digits at all!
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* The weight is arbitrary in that case, but we normally set it to zero.
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*/
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struct NumericShort
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{
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uint16 n_header; /* Sign + display scale + weight */
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NumericDigit n_data[1]; /* Digits */
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};
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struct NumericLong
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{
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uint16 n_sign_dscale; /* Sign + display scale */
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int16 n_weight; /* Weight of 1st digit */
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NumericDigit n_data[1]; /* Digits */
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};
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union NumericChoice
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{
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uint16 n_header; /* Header word */
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struct NumericLong n_long; /* Long form (4-byte header) */
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struct NumericShort n_short; /* Short form (2-byte header) */
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};
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struct NumericData
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{
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int32 vl_len_; /* varlena header (do not touch directly!) */
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union NumericChoice choice; /* choice of format */
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};
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/*
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* Interpretation of high bits.
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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_SHORT 0x8000
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#define NUMERIC_NAN 0xC000
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#define NUMERIC_FLAGBITS(n) ((n)->choice.n_header & NUMERIC_SIGN_MASK)
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#define NUMERIC_IS_NAN(n) (NUMERIC_FLAGBITS(n) == NUMERIC_NAN)
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#define NUMERIC_IS_SHORT(n) (NUMERIC_FLAGBITS(n) == NUMERIC_SHORT)
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#define NUMERIC_HDRSZ (VARHDRSZ + sizeof(uint16) + sizeof(int16))
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#define NUMERIC_HDRSZ_SHORT (VARHDRSZ + sizeof(uint16))
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/*
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* If the flag bits are NUMERIC_SHORT or NUMERIC_NAN, we want the short header;
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* otherwise, we want the long one. Instead of testing against each value, we
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* can just look at the high bit, for a slight efficiency gain.
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*/
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#define NUMERIC_HEADER_SIZE(n) \
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(VARHDRSZ + sizeof(uint16) + \
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(((NUMERIC_FLAGBITS(n) & 0x8000) == 0) ? sizeof(int16) : 0))
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/*
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* Short format definitions.
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*/
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#define NUMERIC_SHORT_SIGN_MASK 0x2000
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#define NUMERIC_SHORT_DSCALE_MASK 0x1F80
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#define NUMERIC_SHORT_DSCALE_SHIFT 7
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#define NUMERIC_SHORT_DSCALE_MAX \
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(NUMERIC_SHORT_DSCALE_MASK >> NUMERIC_SHORT_DSCALE_SHIFT)
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#define NUMERIC_SHORT_WEIGHT_SIGN_MASK 0x0040
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#define NUMERIC_SHORT_WEIGHT_MASK 0x003F
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#define NUMERIC_SHORT_WEIGHT_MAX NUMERIC_SHORT_WEIGHT_MASK
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#define NUMERIC_SHORT_WEIGHT_MIN (-(NUMERIC_SHORT_WEIGHT_MASK+1))
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/*
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* Extract sign, display scale, weight.
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*/
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#define NUMERIC_DSCALE_MASK 0x3FFF
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#define NUMERIC_SIGN(n) \
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(NUMERIC_IS_SHORT(n) ? \
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(((n)->choice.n_short.n_header & NUMERIC_SHORT_SIGN_MASK) ? \
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NUMERIC_NEG : NUMERIC_POS) : NUMERIC_FLAGBITS(n))
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#define NUMERIC_DSCALE(n) (NUMERIC_IS_SHORT((n)) ? \
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((n)->choice.n_short.n_header & NUMERIC_SHORT_DSCALE_MASK) \
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>> NUMERIC_SHORT_DSCALE_SHIFT \
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: ((n)->choice.n_long.n_sign_dscale & NUMERIC_DSCALE_MASK))
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#define NUMERIC_WEIGHT(n) (NUMERIC_IS_SHORT((n)) ? \
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(((n)->choice.n_short.n_header & NUMERIC_SHORT_WEIGHT_SIGN_MASK ? \
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~NUMERIC_SHORT_WEIGHT_MASK : 0) \
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| ((n)->choice.n_short.n_header & NUMERIC_SHORT_WEIGHT_MASK)) \
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: ((n)->choice.n_long.n_weight))
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/* ----------
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* NumericVar is the format we use for arithmetic. The digit-array part
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@ -266,9 +350,14 @@ static void dump_var(const char *str, NumericVar *var);
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#define init_var(v) MemSetAligned(v, 0, sizeof(NumericVar))
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#define NUMERIC_DIGITS(num) ((NumericDigit *)(num)->n_data)
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#define NUMERIC_DIGITS(num) (NUMERIC_IS_SHORT(num) ? \
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(num)->choice.n_short.n_data : (num)->choice.n_long.n_data)
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#define NUMERIC_NDIGITS(num) \
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((VARSIZE(num) - NUMERIC_HDRSZ) / sizeof(NumericDigit))
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((VARSIZE(num) - NUMERIC_HEADER_SIZE(num)) / sizeof(NumericDigit))
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#define NUMERIC_CAN_BE_SHORT(scale,weight) \
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((scale) <= NUMERIC_SHORT_DSCALE_MAX && \
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(weight) <= NUMERIC_SHORT_WEIGHT_MAX && \
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(weight) >= NUMERIC_SHORT_WEIGHT_MIN)
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static void alloc_var(NumericVar *var, int ndigits);
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static void free_var(NumericVar *var);
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@ -652,15 +741,23 @@ numeric (PG_FUNCTION_ARGS)
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/*
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* If the number is certainly in bounds and due to the target scale no
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* rounding could be necessary, just make a copy of the input and modify
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* its scale fields. (Note we assume the existing dscale is honest...)
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* its scale fields, unless the larger scale forces us to abandon the
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* short representation. (Note we assume the existing dscale is honest...)
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*/
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ddigits = (num->n_weight + 1) * DEC_DIGITS;
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if (ddigits <= maxdigits && scale >= NUMERIC_DSCALE(num))
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ddigits = (NUMERIC_WEIGHT(num) + 1) * DEC_DIGITS;
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if (ddigits <= maxdigits && scale >= NUMERIC_DSCALE(num)
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&& (NUMERIC_CAN_BE_SHORT(scale, NUMERIC_WEIGHT(num))
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|| !NUMERIC_IS_SHORT(num)))
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{
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new = (Numeric) palloc(VARSIZE(num));
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memcpy(new, num, VARSIZE(num));
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new->n_sign_dscale = NUMERIC_SIGN(new) |
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((uint16) scale & NUMERIC_DSCALE_MASK);
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if (NUMERIC_IS_SHORT(num))
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new->choice.n_short.n_header =
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(num->choice.n_short.n_header & ~NUMERIC_SHORT_DSCALE_MASK)
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| (scale << NUMERIC_SHORT_DSCALE_SHIFT);
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else
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new->choice.n_long.n_sign_dscale = NUMERIC_SIGN(new) |
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((uint16) scale & NUMERIC_DSCALE_MASK);
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PG_RETURN_NUMERIC(new);
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}
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@ -766,7 +863,11 @@ numeric_abs(PG_FUNCTION_ARGS)
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res = (Numeric) palloc(VARSIZE(num));
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memcpy(res, num, VARSIZE(num));
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res->n_sign_dscale = NUMERIC_POS | NUMERIC_DSCALE(num);
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if (NUMERIC_IS_SHORT(num))
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res->choice.n_short.n_header =
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num->choice.n_short.n_header & ~NUMERIC_SHORT_SIGN_MASK;
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else
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res->choice.n_long.n_sign_dscale = NUMERIC_POS | NUMERIC_DSCALE(num);
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PG_RETURN_NUMERIC(res);
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}
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@ -795,13 +896,18 @@ numeric_uminus(PG_FUNCTION_ARGS)
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* we can identify a ZERO by the fact that there are no digits at all. Do
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* nothing to a zero.
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*/
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if (VARSIZE(num) != NUMERIC_HDRSZ)
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if (NUMERIC_NDIGITS(num) != 0)
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{
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/* Else, flip the sign */
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if (NUMERIC_SIGN(num) == NUMERIC_POS)
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res->n_sign_dscale = NUMERIC_NEG | NUMERIC_DSCALE(num);
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if (NUMERIC_IS_SHORT(num))
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res->choice.n_short.n_header =
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num->choice.n_short.n_header ^ NUMERIC_SHORT_SIGN_MASK;
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else if (NUMERIC_SIGN(num) == NUMERIC_POS)
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res->choice.n_long.n_sign_dscale =
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NUMERIC_NEG | NUMERIC_DSCALE(num);
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else
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res->n_sign_dscale = NUMERIC_POS | NUMERIC_DSCALE(num);
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res->choice.n_long.n_sign_dscale =
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NUMERIC_POS | NUMERIC_DSCALE(num);
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}
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PG_RETURN_NUMERIC(res);
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@ -845,7 +951,7 @@ numeric_sign(PG_FUNCTION_ARGS)
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* The packed format is known to be totally zero digit trimmed always. So
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* we can identify a ZERO by the fact that there are no digits at all.
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*/
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if (VARSIZE(num) == NUMERIC_HDRSZ)
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if (NUMERIC_NDIGITS(num) == 0)
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set_var_from_var(&const_zero, &result);
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else
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{
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@ -1283,9 +1389,9 @@ cmp_numerics(Numeric num1, Numeric num2)
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else
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{
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result = cmp_var_common(NUMERIC_DIGITS(num1), NUMERIC_NDIGITS(num1),
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num1->n_weight, NUMERIC_SIGN(num1),
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NUMERIC_WEIGHT(num1), NUMERIC_SIGN(num1),
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NUMERIC_DIGITS(num2), NUMERIC_NDIGITS(num2),
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num2->n_weight, NUMERIC_SIGN(num2));
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NUMERIC_WEIGHT(num2), NUMERIC_SIGN(num2));
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}
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return result;
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@ -1302,12 +1408,13 @@ hash_numeric(PG_FUNCTION_ARGS)
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int end_offset;
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int i;
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int hash_len;
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NumericDigit *digits;
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/* If it's NaN, don't try to hash the rest of the fields */
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if (NUMERIC_IS_NAN(key))
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PG_RETURN_UINT32(0);
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weight = key->n_weight;
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weight = NUMERIC_WEIGHT(key);
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start_offset = 0;
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end_offset = 0;
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@ -1317,9 +1424,10 @@ hash_numeric(PG_FUNCTION_ARGS)
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* zeros are suppressed, but we're paranoid. Note that we measure the
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* starting and ending offsets in units of NumericDigits, not bytes.
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*/
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digits = NUMERIC_DIGITS(key);
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for (i = 0; i < NUMERIC_NDIGITS(key); i++)
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{
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if (NUMERIC_DIGITS(key)[i] != (NumericDigit) 0)
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if (digits[i] != (NumericDigit) 0)
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break;
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start_offset++;
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@ -1340,7 +1448,7 @@ hash_numeric(PG_FUNCTION_ARGS)
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for (i = NUMERIC_NDIGITS(key) - 1; i >= 0; i--)
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{
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if (NUMERIC_DIGITS(key)[i] != (NumericDigit) 0)
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if (digits[i] != (NumericDigit) 0)
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break;
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end_offset++;
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@ -2536,7 +2644,7 @@ numeric_avg(PG_FUNCTION_ARGS)
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/* SQL92 defines AVG of no values to be NULL */
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/* N is zero iff no digits (cf. numeric_uminus) */
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if (VARSIZE(N) == NUMERIC_HDRSZ)
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if (NUMERIC_NDIGITS(N) == 0)
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PG_RETURN_NULL();
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PG_RETURN_DATUM(DirectFunctionCall2(numeric_div,
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@ -2974,7 +3082,8 @@ dump_numeric(const char *str, Numeric num)
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ndigits = NUMERIC_NDIGITS(num);
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printf("%s: NUMERIC w=%d d=%d ", str, num->n_weight, NUMERIC_DSCALE(num));
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printf("%s: NUMERIC w=%d d=%d ", str,
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NUMERIC_WEIGHT(num), NUMERIC_DSCALE(num));
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switch (NUMERIC_SIGN(num))
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{
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case NUMERIC_POS:
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@ -3265,11 +3374,11 @@ set_var_from_num(Numeric num, NumericVar *dest)
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alloc_var(dest, ndigits);
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dest->weight = num->n_weight;
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dest->weight = NUMERIC_WEIGHT(num);
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dest->sign = NUMERIC_SIGN(num);
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dest->dscale = NUMERIC_DSCALE(num);
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memcpy(dest->digits, num->n_data, ndigits * sizeof(NumericDigit));
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memcpy(dest->digits, NUMERIC_DIGITS(num), ndigits * sizeof(NumericDigit));
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}
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@ -3561,11 +3670,11 @@ make_result(NumericVar *var)
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if (sign == NUMERIC_NAN)
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{
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result = (Numeric) palloc(NUMERIC_HDRSZ);
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result = (Numeric) palloc(NUMERIC_HDRSZ_SHORT);
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SET_VARSIZE(result, NUMERIC_HDRSZ);
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result->n_weight = 0;
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result->n_sign_dscale = NUMERIC_NAN;
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SET_VARSIZE(result, NUMERIC_HDRSZ_SHORT);
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result->choice.n_header = NUMERIC_NAN;
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/* the header word is all we need */
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dump_numeric("make_result()", result);
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return result;
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@ -3592,16 +3701,33 @@ make_result(NumericVar *var)
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}
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/* Build the result */
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len = NUMERIC_HDRSZ + n * sizeof(NumericDigit);
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result = (Numeric) palloc(len);
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SET_VARSIZE(result, len);
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result->n_weight = weight;
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result->n_sign_dscale = sign | (var->dscale & NUMERIC_DSCALE_MASK);
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if (NUMERIC_CAN_BE_SHORT(var->dscale, weight))
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{
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len = NUMERIC_HDRSZ_SHORT + n * sizeof(NumericDigit);
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result = (Numeric) palloc(len);
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SET_VARSIZE(result, len);
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result->choice.n_short.n_header =
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(sign == NUMERIC_NEG ? (NUMERIC_SHORT | NUMERIC_SHORT_SIGN_MASK)
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: NUMERIC_SHORT)
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| (var->dscale << NUMERIC_SHORT_DSCALE_SHIFT)
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| (weight < 0 ? NUMERIC_SHORT_WEIGHT_SIGN_MASK : 0)
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| (weight & NUMERIC_SHORT_WEIGHT_MASK);
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}
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else
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{
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len = NUMERIC_HDRSZ + n * sizeof(NumericDigit);
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result = (Numeric) palloc(len);
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SET_VARSIZE(result, len);
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result->choice.n_long.n_sign_dscale =
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sign | (var->dscale & NUMERIC_DSCALE_MASK);
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result->choice.n_long.n_weight = weight;
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}
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memcpy(result->n_data, digits, n * sizeof(NumericDigit));
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memcpy(NUMERIC_DIGITS(result), digits, n * sizeof(NumericDigit));
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Assert(NUMERIC_NDIGITS(result) == n);
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/* Check for overflow of int16 fields */
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if (result->n_weight != weight ||
|
||||
if (NUMERIC_WEIGHT(result) != weight ||
|
||||
NUMERIC_DSCALE(result) != var->dscale)
|
||||
ereport(ERROR,
|
||||
(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
|
||||
|
||||
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Reference in New Issue
Block a user