These allow better control of trailing zeroes in numeric values.
Pavel Stehule, based on an old proposal of Marko Tiikkaja's;
review by Karl Pinc
Discussion: https://postgr.es/m/CAFj8pRDjs-navGASeF0Wk74N36YGFJ+v=Ok9_knRa7vDc-qugg@mail.gmail.com
<entry><literal>6.0000000000</literal></entry>
</row>
+ <row>
+ <entry>
+ <indexterm>
+ <primary>min_scale</primary>
+ </indexterm>
+ <literal><function>min_scale(<type>numeric</type>)</function></literal>
+ </entry>
+ <entry><type>integer</type></entry>
+ <entry>minimum scale (number of fractional decimal digits) needed
+ to represent the supplied value</entry>
+ <entry><literal>min_scale(8.4100)</literal></entry>
+ <entry><literal>2</literal></entry>
+ </row>
+
<row>
<entry>
<indexterm>
</entry>
<entry><type>integer</type></entry>
<entry>scale of the argument (the number of decimal digits in the fractional part)</entry>
- <entry><literal>scale(8.41)</literal></entry>
- <entry><literal>2</literal></entry>
+ <entry><literal>scale(8.4100)</literal></entry>
+ <entry><literal>4</literal></entry>
</row>
<row>
<entry><literal>1.4142135623731</literal></entry>
</row>
+ <row>
+ <entry>
+ <indexterm>
+ <primary>trim_scale</primary>
+ </indexterm>
+ <literal><function>trim_scale(<type>numeric</type>)</function></literal>
+ </entry>
+ <entry><type>numeric</type></entry>
+ <entry>reduce the scale (number of fractional decimal digits) by
+ removing trailing zeroes</entry>
+ <entry><literal>trim_scale(8.4100)</literal></entry>
+ <entry><literal>8.41</literal></entry>
+ </row>
+
<row>
<entry>
<indexterm>
PG_RETURN_INT32(NUMERIC_DSCALE(num));
}
+/*
+ * Calculate minimum scale for value.
+ */
+static int
+get_min_scale(NumericVar *var)
+{
+ int min_scale;
+ int last_digit_pos;
+
+ /*
+ * Ordinarily, the input value will be "stripped" so that the last
+ * NumericDigit is nonzero. But we don't want to get into an infinite
+ * loop if it isn't, so explicitly find the last nonzero digit.
+ */
+ last_digit_pos = var->ndigits - 1;
+ while (last_digit_pos >= 0 &&
+ var->digits[last_digit_pos] == 0)
+ last_digit_pos--;
+
+ if (last_digit_pos >= 0)
+ {
+ /* compute min_scale assuming that last ndigit has no zeroes */
+ min_scale = (last_digit_pos - var->weight) * DEC_DIGITS;
+
+ /*
+ * We could get a negative result if there are no digits after the
+ * decimal point. In this case the min_scale must be zero.
+ */
+ if (min_scale > 0)
+ {
+ /*
+ * Reduce min_scale if trailing digit(s) in last NumericDigit are
+ * zero.
+ */
+ NumericDigit last_digit = var->digits[last_digit_pos];
+
+ while (last_digit % 10 == 0)
+ {
+ min_scale--;
+ last_digit /= 10;
+ }
+ }
+ else
+ min_scale = 0;
+ }
+ else
+ min_scale = 0; /* result if input is zero */
+
+ return min_scale;
+}
+
+/*
+ * Returns minimum scale required to represent supplied value without loss.
+ */
+Datum
+numeric_min_scale(PG_FUNCTION_ARGS)
+{
+ Numeric num = PG_GETARG_NUMERIC(0);
+ NumericVar arg;
+ int min_scale;
+
+ if (NUMERIC_IS_NAN(num))
+ PG_RETURN_NULL();
+
+ init_var_from_num(num, &arg);
+ min_scale = get_min_scale(&arg);
+ free_var(&arg);
+
+ PG_RETURN_INT32(min_scale);
+}
+
+/*
+ * Reduce scale of numeric value to represent supplied value without loss.
+ */
+Datum
+numeric_trim_scale(PG_FUNCTION_ARGS)
+{
+ Numeric num = PG_GETARG_NUMERIC(0);
+ Numeric res;
+ NumericVar result;
+
+ if (NUMERIC_IS_NAN(num))
+ PG_RETURN_NUMERIC(make_result(&const_nan));
+
+ init_var_from_num(num, &result);
+ result.dscale = get_min_scale(&result);
+ res = make_result(&result);
+ free_var(&result);
+
+ PG_RETURN_NUMERIC(res);
+}
/* ----------------------------------------------------------------------
*/
/* yyyymmddN */
-#define CATALOG_VERSION_NO 201911241
+#define CATALOG_VERSION_NO 202001061
#endif
{ oid => '3281', descr => 'number of decimal digits in the fractional part',
proname => 'scale', prorettype => 'int4', proargtypes => 'numeric',
prosrc => 'numeric_scale' },
+{ oid => '8389', descr => 'minimum scale needed to represent the value',
+ proname => 'min_scale', prorettype => 'int4', proargtypes => 'numeric',
+ prosrc => 'numeric_min_scale' },
+{ oid => '8390',
+ descr => 'numeric with minimum scale needed to represent the value',
+ proname => 'trim_scale', prorettype => 'numeric', proargtypes => 'numeric',
+ prosrc => 'numeric_trim_scale' },
{ oid => '1740', descr => 'convert int4 to numeric',
proname => 'numeric', prorettype => 'numeric', proargtypes => 'int4',
prosrc => 'int4_numeric' },
15
(1 row)
+--
+-- Tests for min_scale()
+--
+select min_scale(numeric 'NaN') is NULL; -- should be true
+ ?column?
+----------
+ t
+(1 row)
+
+select min_scale(0); -- no digits
+ min_scale
+-----------
+ 0
+(1 row)
+
+select min_scale(0.00); -- no digits again
+ min_scale
+-----------
+ 0
+(1 row)
+
+select min_scale(1.0); -- no scale
+ min_scale
+-----------
+ 0
+(1 row)
+
+select min_scale(1.1); -- scale 1
+ min_scale
+-----------
+ 1
+(1 row)
+
+select min_scale(1.12); -- scale 2
+ min_scale
+-----------
+ 2
+(1 row)
+
+select min_scale(1.123); -- scale 3
+ min_scale
+-----------
+ 3
+(1 row)
+
+select min_scale(1.1234); -- scale 4, filled digit
+ min_scale
+-----------
+ 4
+(1 row)
+
+select min_scale(1.12345); -- scale 5, 2 NDIGITS
+ min_scale
+-----------
+ 5
+(1 row)
+
+select min_scale(1.1000); -- 1 pos in NDIGITS
+ min_scale
+-----------
+ 1
+(1 row)
+
+select min_scale(1e100); -- very big number
+ min_scale
+-----------
+ 0
+(1 row)
+
+--
+-- Tests for trim_scale()
+--
+select trim_scale(numeric 'NaN');
+ trim_scale
+------------
+ NaN
+(1 row)
+
+select trim_scale(1.120);
+ trim_scale
+------------
+ 1.12
+(1 row)
+
+select trim_scale(0);
+ trim_scale
+------------
+ 0
+(1 row)
+
+select trim_scale(0.00);
+ trim_scale
+------------
+ 0
+(1 row)
+
+select trim_scale(1.1234500);
+ trim_scale
+------------
+ 1.12345
+(1 row)
+
+select trim_scale(110123.12475871856128000);
+ trim_scale
+-----------------------
+ 110123.12475871856128
+(1 row)
+
+select trim_scale(-1123.124718561280000000);
+ trim_scale
+-------------------
+ -1123.12471856128
+(1 row)
+
+select trim_scale(-13.00000000000000000000);
+ trim_scale
+------------
+ -13
+(1 row)
+
+select trim_scale(1e100);
+ trim_scale
+-------------------------------------------------------------------------------------------------------
+ 10000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
+(1 row)
+
--
-- Tests for SUM()
--
select scale(-1123.12471856128);
select scale(-13.000000000000000);
+--
+-- Tests for min_scale()
+--
+
+select min_scale(numeric 'NaN') is NULL; -- should be true
+select min_scale(0); -- no digits
+select min_scale(0.00); -- no digits again
+select min_scale(1.0); -- no scale
+select min_scale(1.1); -- scale 1
+select min_scale(1.12); -- scale 2
+select min_scale(1.123); -- scale 3
+select min_scale(1.1234); -- scale 4, filled digit
+select min_scale(1.12345); -- scale 5, 2 NDIGITS
+select min_scale(1.1000); -- 1 pos in NDIGITS
+select min_scale(1e100); -- very big number
+
+--
+-- Tests for trim_scale()
+--
+
+select trim_scale(numeric 'NaN');
+select trim_scale(1.120);
+select trim_scale(0);
+select trim_scale(0.00);
+select trim_scale(1.1234500);
+select trim_scale(110123.12475871856128000);
+select trim_scale(-1123.124718561280000000);
+select trim_scale(-13.00000000000000000000);
+select trim_scale(1e100);
+
--
-- Tests for SUM()
--
projects / users / gsingh / postgres.git / commitdiff