* Copyright (c) 1998-2010, PostgreSQL Global Development Group
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/utils/adt/numeric.c,v 1.124 2010/07/30 04:30:23 rhaas Exp $
+ * $PostgreSQL: pgsql/src/backend/utils/adt/numeric.c,v 1.125 2010/08/03 23:09:29 rhaas Exp $
*
*-------------------------------------------------------------------------
*/
#include "utils/int8.h"
#include "utils/numeric.h"
-/*
- * Sign values and macros to deal with packing/unpacking n_sign_dscale
- */
-#define NUMERIC_SIGN_MASK 0xC000
-#define NUMERIC_POS 0x0000
-#define NUMERIC_NEG 0x4000
-#define NUMERIC_NAN 0xC000
-#define NUMERIC_DSCALE_MASK 0x3FFF
-#define NUMERIC_SIGN(n) ((n)->n_sign_dscale & NUMERIC_SIGN_MASK)
-#define NUMERIC_DSCALE(n) ((n)->n_sign_dscale & NUMERIC_DSCALE_MASK)
-#define NUMERIC_IS_NAN(n) (NUMERIC_SIGN(n) != NUMERIC_POS && \
- NUMERIC_SIGN(n) != NUMERIC_NEG)
-#define NUMERIC_HDRSZ (VARHDRSZ + sizeof(uint16) + sizeof(int16))
-
-
-/*
- * The Numeric data type stored in the database
- *
- * NOTE: by convention, values in the packed form have been stripped of
- * all leading and trailing zero digits (where a "digit" is of base NBASE).
- * In particular, if the value is zero, there will be no digits at all!
- * The weight is arbitrary in that case, but we normally set it to zero.
- */
-struct NumericData
-{
- int32 vl_len_; /* varlena header (do not touch directly!) */
- uint16 n_sign_dscale; /* Sign + display scale */
- int16 n_weight; /* Weight of 1st digit */
- char n_data[1]; /* Digits (really array of NumericDigit) */
-};
-
-
/* ----------
* Uncomment the following to enable compilation of dump_numeric()
* and dump_var() and to get a dump of any result produced by make_result().
typedef int16 NumericDigit;
#endif
+/*
+ * The Numeric type as stored on disk.
+ *
+ * If the high bits of the first word of a NumericChoice (n_header, or
+ * n_short.n_header, or n_long.n_sign_dscale) are NUMERIC_SHORT, then the
+ * numeric follows the NumericShort format; if they are NUMERIC_POS or
+ * NUMERIC_NEG, it follows the NumericLong format. If they are NUMERIC_NAN,
+ * it is a NaN. We currently always store a NaN using just two bytes (i.e.
+ * only n_header), but previous releases used only the NumericLong format,
+ * so we might find 4-byte NaNs on disk if a database has been migrated using
+ * pg_upgrade. In either case, when the high bits indicate a NaN, the
+ * remaining bits are never examined. Currently, we always initialize these
+ * to zero, but it might be possible to use them for some other purpose in
+ * the future.
+ *
+ * In the NumericShort format, the remaining 14 bits of the header word
+ * (n_short.n_header) are allocated as follows: 1 for sign (positive or
+ * negative), 6 for dynamic scale, and 7 for weight. In practice, most
+ * commonly-encountered values can be represented this way.
+ *
+ * In the NumericLong format, the remaining 14 bits of the header word
+ * (n_long.n_sign_dscale) represent the display scale; and the weight is
+ * stored separately in n_weight.
+ *
+ * NOTE: by convention, values in the packed form have been stripped of
+ * all leading and trailing zero digits (where a "digit" is of base NBASE).
+ * In particular, if the value is zero, there will be no digits at all!
+ * The weight is arbitrary in that case, but we normally set it to zero.
+ */
+
+struct NumericShort
+{
+ uint16 n_header; /* Sign + display scale + weight */
+ NumericDigit n_data[1]; /* Digits */
+};
+
+struct NumericLong
+{
+ uint16 n_sign_dscale; /* Sign + display scale */
+ int16 n_weight; /* Weight of 1st digit */
+ NumericDigit n_data[1]; /* Digits */
+};
+
+union NumericChoice
+{
+ uint16 n_header; /* Header word */
+ struct NumericLong n_long; /* Long form (4-byte header) */
+ struct NumericShort n_short; /* Short form (2-byte header) */
+};
+
+struct NumericData
+{
+ int32 vl_len_; /* varlena header (do not touch directly!) */
+ union NumericChoice choice; /* choice of format */
+};
+
+
+/*
+ * Interpretation of high bits.
+ */
+
+#define NUMERIC_SIGN_MASK 0xC000
+#define NUMERIC_POS 0x0000
+#define NUMERIC_NEG 0x4000
+#define NUMERIC_SHORT 0x8000
+#define NUMERIC_NAN 0xC000
+
+#define NUMERIC_FLAGBITS(n) ((n)->choice.n_header & NUMERIC_SIGN_MASK)
+#define NUMERIC_IS_NAN(n) (NUMERIC_FLAGBITS(n) == NUMERIC_NAN)
+#define NUMERIC_IS_SHORT(n) (NUMERIC_FLAGBITS(n) == NUMERIC_SHORT)
+
+#define NUMERIC_HDRSZ (VARHDRSZ + sizeof(uint16) + sizeof(int16))
+#define NUMERIC_HDRSZ_SHORT (VARHDRSZ + sizeof(uint16))
+
+/*
+ * If the flag bits are NUMERIC_SHORT or NUMERIC_NAN, we want the short header;
+ * otherwise, we want the long one. Instead of testing against each value, we
+ * can just look at the high bit, for a slight efficiency gain.
+ */
+#define NUMERIC_HEADER_SIZE(n) \
+ (VARHDRSZ + sizeof(uint16) + \
+ (((NUMERIC_FLAGBITS(n) & 0x8000) == 0) ? sizeof(int16) : 0))
+
+/*
+ * Short format definitions.
+ */
+
+#define NUMERIC_SHORT_SIGN_MASK 0x2000
+#define NUMERIC_SHORT_DSCALE_MASK 0x1F80
+#define NUMERIC_SHORT_DSCALE_SHIFT 7
+#define NUMERIC_SHORT_DSCALE_MAX \
+ (NUMERIC_SHORT_DSCALE_MASK >> NUMERIC_SHORT_DSCALE_SHIFT)
+#define NUMERIC_SHORT_WEIGHT_SIGN_MASK 0x0040
+#define NUMERIC_SHORT_WEIGHT_MASK 0x003F
+#define NUMERIC_SHORT_WEIGHT_MAX NUMERIC_SHORT_WEIGHT_MASK
+#define NUMERIC_SHORT_WEIGHT_MIN (-(NUMERIC_SHORT_WEIGHT_MASK+1))
+
+/*
+ * Extract sign, display scale, weight.
+ */
+
+#define NUMERIC_DSCALE_MASK 0x3FFF
+
+#define NUMERIC_SIGN(n) \
+ (NUMERIC_IS_SHORT(n) ? \
+ (((n)->choice.n_short.n_header & NUMERIC_SHORT_SIGN_MASK) ? \
+ NUMERIC_NEG : NUMERIC_POS) : NUMERIC_FLAGBITS(n))
+#define NUMERIC_DSCALE(n) (NUMERIC_IS_SHORT((n)) ? \
+ ((n)->choice.n_short.n_header & NUMERIC_SHORT_DSCALE_MASK) \
+ >> NUMERIC_SHORT_DSCALE_SHIFT \
+ : ((n)->choice.n_long.n_sign_dscale & NUMERIC_DSCALE_MASK))
+#define NUMERIC_WEIGHT(n) (NUMERIC_IS_SHORT((n)) ? \
+ (((n)->choice.n_short.n_header & NUMERIC_SHORT_WEIGHT_SIGN_MASK ? \
+ ~NUMERIC_SHORT_WEIGHT_MASK : 0) \
+ | ((n)->choice.n_short.n_header & NUMERIC_SHORT_WEIGHT_MASK)) \
+ : ((n)->choice.n_long.n_weight))
/* ----------
* NumericVar is the format we use for arithmetic. The digit-array part
#define init_var(v) MemSetAligned(v, 0, sizeof(NumericVar))
-#define NUMERIC_DIGITS(num) ((NumericDigit *)(num)->n_data)
+#define NUMERIC_DIGITS(num) (NUMERIC_IS_SHORT(num) ? \
+ (num)->choice.n_short.n_data : (num)->choice.n_long.n_data)
#define NUMERIC_NDIGITS(num) \
- ((VARSIZE(num) - NUMERIC_HDRSZ) / sizeof(NumericDigit))
+ ((VARSIZE(num) - NUMERIC_HEADER_SIZE(num)) / sizeof(NumericDigit))
+#define NUMERIC_CAN_BE_SHORT(scale,weight) \
+ ((scale) <= NUMERIC_SHORT_DSCALE_MAX && \
+ (weight) <= NUMERIC_SHORT_WEIGHT_MAX && \
+ (weight) >= NUMERIC_SHORT_WEIGHT_MIN)
static void alloc_var(NumericVar *var, int ndigits);
static void free_var(NumericVar *var);
/*
* If the number is certainly in bounds and due to the target scale no
* rounding could be necessary, just make a copy of the input and modify
- * its scale fields. (Note we assume the existing dscale is honest...)
+ * its scale fields, unless the larger scale forces us to abandon the
+ * short representation. (Note we assume the existing dscale is honest...)
*/
- ddigits = (num->n_weight + 1) * DEC_DIGITS;
- if (ddigits <= maxdigits && scale >= NUMERIC_DSCALE(num))
+ ddigits = (NUMERIC_WEIGHT(num) + 1) * DEC_DIGITS;
+ if (ddigits <= maxdigits && scale >= NUMERIC_DSCALE(num)
+ && (NUMERIC_CAN_BE_SHORT(scale, NUMERIC_WEIGHT(num))
+ || !NUMERIC_IS_SHORT(num)))
{
new = (Numeric) palloc(VARSIZE(num));
memcpy(new, num, VARSIZE(num));
- new->n_sign_dscale = NUMERIC_SIGN(new) |
- ((uint16) scale & NUMERIC_DSCALE_MASK);
+ if (NUMERIC_IS_SHORT(num))
+ new->choice.n_short.n_header =
+ (num->choice.n_short.n_header & ~NUMERIC_SHORT_DSCALE_MASK)
+ | (scale << NUMERIC_SHORT_DSCALE_SHIFT);
+ else
+ new->choice.n_long.n_sign_dscale = NUMERIC_SIGN(new) |
+ ((uint16) scale & NUMERIC_DSCALE_MASK);
PG_RETURN_NUMERIC(new);
}
res = (Numeric) palloc(VARSIZE(num));
memcpy(res, num, VARSIZE(num));
- res->n_sign_dscale = NUMERIC_POS | NUMERIC_DSCALE(num);
+ if (NUMERIC_IS_SHORT(num))
+ res->choice.n_short.n_header =
+ num->choice.n_short.n_header & ~NUMERIC_SHORT_SIGN_MASK;
+ else
+ res->choice.n_long.n_sign_dscale = NUMERIC_POS | NUMERIC_DSCALE(num);
PG_RETURN_NUMERIC(res);
}
* we can identify a ZERO by the fact that there are no digits at all. Do
* nothing to a zero.
*/
- if (VARSIZE(num) != NUMERIC_HDRSZ)
+ if (NUMERIC_NDIGITS(num) != 0)
{
/* Else, flip the sign */
- if (NUMERIC_SIGN(num) == NUMERIC_POS)
- res->n_sign_dscale = NUMERIC_NEG | NUMERIC_DSCALE(num);
+ if (NUMERIC_IS_SHORT(num))
+ res->choice.n_short.n_header =
+ num->choice.n_short.n_header ^ NUMERIC_SHORT_SIGN_MASK;
+ else if (NUMERIC_SIGN(num) == NUMERIC_POS)
+ res->choice.n_long.n_sign_dscale =
+ NUMERIC_NEG | NUMERIC_DSCALE(num);
else
- res->n_sign_dscale = NUMERIC_POS | NUMERIC_DSCALE(num);
+ res->choice.n_long.n_sign_dscale =
+ NUMERIC_POS | NUMERIC_DSCALE(num);
}
PG_RETURN_NUMERIC(res);
* The packed format is known to be totally zero digit trimmed always. So
* we can identify a ZERO by the fact that there are no digits at all.
*/
- if (VARSIZE(num) == NUMERIC_HDRSZ)
+ if (NUMERIC_NDIGITS(num) == 0)
set_var_from_var(&const_zero, &result);
else
{
else
{
result = cmp_var_common(NUMERIC_DIGITS(num1), NUMERIC_NDIGITS(num1),
- num1->n_weight, NUMERIC_SIGN(num1),
+ NUMERIC_WEIGHT(num1), NUMERIC_SIGN(num1),
NUMERIC_DIGITS(num2), NUMERIC_NDIGITS(num2),
- num2->n_weight, NUMERIC_SIGN(num2));
+ NUMERIC_WEIGHT(num2), NUMERIC_SIGN(num2));
}
return result;
int end_offset;
int i;
int hash_len;
+ NumericDigit *digits;
/* If it's NaN, don't try to hash the rest of the fields */
if (NUMERIC_IS_NAN(key))
PG_RETURN_UINT32(0);
- weight = key->n_weight;
+ weight = NUMERIC_WEIGHT(key);
start_offset = 0;
end_offset = 0;
* zeros are suppressed, but we're paranoid. Note that we measure the
* starting and ending offsets in units of NumericDigits, not bytes.
*/
+ digits = NUMERIC_DIGITS(key);
for (i = 0; i < NUMERIC_NDIGITS(key); i++)
{
- if (NUMERIC_DIGITS(key)[i] != (NumericDigit) 0)
+ if (digits[i] != (NumericDigit) 0)
break;
start_offset++;
for (i = NUMERIC_NDIGITS(key) - 1; i >= 0; i--)
{
- if (NUMERIC_DIGITS(key)[i] != (NumericDigit) 0)
+ if (digits[i] != (NumericDigit) 0)
break;
end_offset++;
/* SQL92 defines AVG of no values to be NULL */
/* N is zero iff no digits (cf. numeric_uminus) */
- if (VARSIZE(N) == NUMERIC_HDRSZ)
+ if (NUMERIC_NDIGITS(N) == 0)
PG_RETURN_NULL();
PG_RETURN_DATUM(DirectFunctionCall2(numeric_div,
ndigits = NUMERIC_NDIGITS(num);
- printf("%s: NUMERIC w=%d d=%d ", str, num->n_weight, NUMERIC_DSCALE(num));
+ printf("%s: NUMERIC w=%d d=%d ", str,
+ NUMERIC_WEIGHT(num), NUMERIC_DSCALE(num));
switch (NUMERIC_SIGN(num))
{
case NUMERIC_POS:
alloc_var(dest, ndigits);
- dest->weight = num->n_weight;
+ dest->weight = NUMERIC_WEIGHT(num);
dest->sign = NUMERIC_SIGN(num);
dest->dscale = NUMERIC_DSCALE(num);
- memcpy(dest->digits, num->n_data, ndigits * sizeof(NumericDigit));
+ memcpy(dest->digits, NUMERIC_DIGITS(num), ndigits * sizeof(NumericDigit));
}
if (sign == NUMERIC_NAN)
{
- result = (Numeric) palloc(NUMERIC_HDRSZ);
+ result = (Numeric) palloc(NUMERIC_HDRSZ_SHORT);
- SET_VARSIZE(result, NUMERIC_HDRSZ);
- result->n_weight = 0;
- result->n_sign_dscale = NUMERIC_NAN;
+ SET_VARSIZE(result, NUMERIC_HDRSZ_SHORT);
+ result->choice.n_header = NUMERIC_NAN;
+ /* the header word is all we need */
dump_numeric("make_result()", result);
return result;
}
/* Build the result */
- len = NUMERIC_HDRSZ + n * sizeof(NumericDigit);
- result = (Numeric) palloc(len);
- SET_VARSIZE(result, len);
- result->n_weight = weight;
- result->n_sign_dscale = sign | (var->dscale & NUMERIC_DSCALE_MASK);
+ if (NUMERIC_CAN_BE_SHORT(var->dscale, weight))
+ {
+ len = NUMERIC_HDRSZ_SHORT + n * sizeof(NumericDigit);
+ result = (Numeric) palloc(len);
+ SET_VARSIZE(result, len);
+ result->choice.n_short.n_header =
+ (sign == NUMERIC_NEG ? (NUMERIC_SHORT | NUMERIC_SHORT_SIGN_MASK)
+ : NUMERIC_SHORT)
+ | (var->dscale << NUMERIC_SHORT_DSCALE_SHIFT)
+ | (weight < 0 ? NUMERIC_SHORT_WEIGHT_SIGN_MASK : 0)
+ | (weight & NUMERIC_SHORT_WEIGHT_MASK);
+ }
+ else
+ {
+ len = NUMERIC_HDRSZ + n * sizeof(NumericDigit);
+ result = (Numeric) palloc(len);
+ SET_VARSIZE(result, len);
+ result->choice.n_long.n_sign_dscale =
+ sign | (var->dscale & NUMERIC_DSCALE_MASK);
+ result->choice.n_long.n_weight = weight;
+ }
- memcpy(result->n_data, digits, n * sizeof(NumericDigit));
+ memcpy(NUMERIC_DIGITS(result), digits, n * sizeof(NumericDigit));
+ Assert(NUMERIC_NDIGITS(result) == n);
/* Check for overflow of int16 fields */
- 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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