-
Notifications
You must be signed in to change notification settings - Fork 7
/
array_to_percentile.c
129 lines (102 loc) · 3.28 KB
/
array_to_percentile.c
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
Datum array_to_percentile(PG_FUNCTION_ARGS);
PG_FUNCTION_INFO_V1(array_to_percentile);
/**
* Returns a percentile from an array of numbers.
* by Paul A. Jungwirth
*/
Datum
array_to_percentile(PG_FUNCTION_ARGS)
{
// Our arguments:
ArrayType *vals;
// The array element type:
Oid valsType;
// The array element type widths for our input array:
int16 valsTypeWidth;
// The array element type "is passed by value" flags (not really used):
bool valsTypeByValue;
// The array element type alignment codes (not really used):
char valsTypeAlignmentCode;
// The array contents, as PostgreSQL "Datum" objects:
Datum *valsContent;
// List of "is null" flags for the array contents (not used):
bool *valsNullFlags;
// The size of the input array:
int valsLength;
float8 *floatVals;
int i;
float8 perc;
float8 floatPos;
float8 v = 0;
if (PG_ARGISNULL(0) || PG_ARGISNULL(1)) {
ereport(ERROR, (errmsg("Null arguments not accepted")));
}
vals = PG_GETARG_ARRAYTYPE_P(0);
if (ARR_NDIM(vals) == 0) {
PG_RETURN_NULL();
}
if (ARR_NDIM(vals) > 1) {
ereport(ERROR, (errmsg("One-dimesional arrays are required")));
}
if (array_contains_nulls(vals)) {
ereport(ERROR, (errmsg("Array contains null elements")));
}
// Determine the array element types.
valsType = ARR_ELEMTYPE(vals);
if (valsType != INT2OID &&
valsType != INT4OID &&
valsType != INT8OID &&
valsType != FLOAT4OID &&
valsType != FLOAT8OID) {
ereport(ERROR, (errmsg("Percentile subject must be SMALLINT, INTEGER, BIGINT, REAL, or DOUBLE PRECISION values")));
}
perc = PG_GETARG_FLOAT8(1);
if (perc < 0 || perc > 1) {
ereport(ERROR, (errmsg("Percent must be between 0 and 1")));
}
valsLength = (ARR_DIMS(vals))[0];
get_typlenbyvalalign(valsType, &valsTypeWidth, &valsTypeByValue, &valsTypeAlignmentCode);
// Extract the array contents (as Datum objects).
deconstruct_array(vals, valsType, valsTypeWidth, valsTypeByValue, valsTypeAlignmentCode,
&valsContent, &valsNullFlags, &valsLength);
// Compute the percentile:
floatVals = palloc(sizeof(float8) * valsLength);
switch (valsType) {
case INT2OID:
for (i = 0; i < valsLength; i++) {
floatVals[i] = DatumGetInt16(valsContent[i]);
}
break;
case INT4OID:
for (i = 0; i < valsLength; i++) {
floatVals[i] = DatumGetInt32(valsContent[i]);
}
break;
case INT8OID:
for (i = 0; i < valsLength; i++) {
floatVals[i] = DatumGetInt64(valsContent[i]);
}
break;
case FLOAT4OID:
for (i = 0; i < valsLength; i++) {
floatVals[i] = DatumGetFloat4(valsContent[i]);
}
break;
case FLOAT8OID:
for (i = 0; i < valsLength; i++) {
floatVals[i] = DatumGetFloat8(valsContent[i]);
}
break;
default:
ereport(ERROR, (errmsg("Percentile subject must be SMALLINT, INTEGER, BIGINT, REAL, or DOUBLE PRECISION values")));
break;
}
// TODO: Could use select_kth_value here instead of sorting?:
qsort(floatVals, valsLength, sizeof(float8), compare_float8);
floatPos = (valsLength - 1) * perc;
v = floatVals[(int)floatPos];
if (floorl(floatPos) != floatPos) {
v += (floatVals[(int)floatPos + 1] - v) * (floatPos - floorl(floatPos));
}
PG_RETURN_FLOAT8(v);
}