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array_to_min_max.c
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array_to_min_max.c
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Datum array_to_min_max(PG_FUNCTION_ARGS);
PG_FUNCTION_INFO_V1(array_to_min_max);
/**
* Returns a min and max from an (unsorted) array of numbers.
* by Paul A. Jungwirth
*/
Datum
array_to_min_max(PG_FUNCTION_ARGS)
{
// Our arguments:
ArrayType *vals;
// The array element type:
Oid valsType;
// The array element type widths for our input array:
int16 valsTypeWidth;
int16 retTypeWidth;
// The array element type "is passed by value" flags (not really used):
bool valsTypeByValue;
bool retTypeByValue;
// The array element type alignment codes (not really used):
char valsTypeAlignmentCode;
char retTypeAlignmentCode;
// The array contents, as PostgreSQL "Datum" objects:
Datum *valsContent;
Datum *retContent;
// List of "is null" flags for the array contents (not used):
bool *valsNullFlags;
// The size of the input array:
int valsLength;
// The output array:
ArrayType* retArray;
int i;
pgnum minV, maxV;
if (PG_ARGISNULL(0)) {
ereport(ERROR, (errmsg("Null arrays 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("Minmax subject must be SMALLINT, INTEGER, BIGINT, REAL, or DOUBLE PRECISION values")));
}
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);
if (valsLength == 0) PG_RETURN_NULL();
// Compute the max.
retContent = palloc0(sizeof(Datum) * 2);
switch (valsType) {
case INT2OID:
minV.i16 = DatumGetInt16(valsContent[0]);
maxV.i16 = DatumGetInt16(valsContent[0]);
for (i = 1; i < valsLength; i++) {
if (DatumGetInt16(valsContent[i]) < minV.i16) minV.i16 = DatumGetInt16(valsContent[i]);
if (DatumGetInt16(valsContent[i]) > maxV.i16) maxV.i16 = DatumGetInt16(valsContent[i]);
}
retContent[0] = Int16GetDatum(minV.i16);
retContent[1] = Int16GetDatum(maxV.i16);
get_typlenbyvalalign(INT2OID, &retTypeWidth, &retTypeByValue, &retTypeAlignmentCode);
retArray = construct_array(retContent, 2, INT2OID, retTypeWidth, retTypeByValue, retTypeAlignmentCode);
break;
case INT4OID:
minV.i32 = DatumGetInt32(valsContent[0]);
maxV.i32 = DatumGetInt32(valsContent[0]);
for (i = 1; i < valsLength; i++) {
if (DatumGetInt32(valsContent[i]) < minV.i32) minV.i32 = DatumGetInt32(valsContent[i]);
if (DatumGetInt32(valsContent[i]) > maxV.i32) maxV.i32 = DatumGetInt32(valsContent[i]);
}
retContent[0] = Int32GetDatum(minV.i32);
retContent[1] = Int32GetDatum(maxV.i32);
get_typlenbyvalalign(INT4OID, &retTypeWidth, &retTypeByValue, &retTypeAlignmentCode);
retArray = construct_array(retContent, 2, INT4OID, retTypeWidth, retTypeByValue, retTypeAlignmentCode);
break;
case INT8OID:
minV.i64 = DatumGetInt64(valsContent[0]);
maxV.i64 = DatumGetInt64(valsContent[0]);
for (i = 1; i < valsLength; i++) {
if (DatumGetInt64(valsContent[i]) < minV.i64) minV.i64 = DatumGetInt64(valsContent[i]);
if (DatumGetInt64(valsContent[i]) > maxV.i64) maxV.i64 = DatumGetInt64(valsContent[i]);
}
retContent[0] = Int64GetDatum(minV.i64);
retContent[1] = Int64GetDatum(maxV.i64);
get_typlenbyvalalign(INT8OID, &retTypeWidth, &retTypeByValue, &retTypeAlignmentCode);
retArray = construct_array(retContent, 2, INT8OID, retTypeWidth, retTypeByValue, retTypeAlignmentCode);
break;
case FLOAT4OID:
minV.f4 = DatumGetFloat4(valsContent[0]);
maxV.f4 = DatumGetFloat4(valsContent[0]);
for (i = 1; i < valsLength; i++) {
if (DatumGetFloat4(valsContent[i]) < minV.f4) minV.f4 = DatumGetFloat4(valsContent[i]);
if (DatumGetFloat4(valsContent[i]) > maxV.f4) maxV.f4 = DatumGetFloat4(valsContent[i]);
}
retContent[0] = Float4GetDatum(minV.f4);
retContent[1] = Float4GetDatum(maxV.f4);
get_typlenbyvalalign(FLOAT4OID, &retTypeWidth, &retTypeByValue, &retTypeAlignmentCode);
retArray = construct_array(retContent, 2, FLOAT4OID, retTypeWidth, retTypeByValue, retTypeAlignmentCode);
break;
case FLOAT8OID:
minV.f8 = DatumGetFloat8(valsContent[0]);
maxV.f8 = DatumGetFloat8(valsContent[0]);
for (i = 1; i < valsLength; i++) {
if (DatumGetFloat8(valsContent[i]) < minV.f8) minV.f8 = DatumGetFloat8(valsContent[i]);
if (DatumGetFloat8(valsContent[i]) > maxV.f8) maxV.f8 = DatumGetFloat8(valsContent[i]);
}
retContent[0] = Float8GetDatum(minV.f8);
retContent[1] = Float8GetDatum(maxV.f8);
get_typlenbyvalalign(FLOAT8OID, &retTypeWidth, &retTypeByValue, &retTypeAlignmentCode);
retArray = construct_array(retContent, 2, FLOAT8OID, retTypeWidth, retTypeByValue, retTypeAlignmentCode);
break;
default:
ereport(ERROR, (errmsg("Minmax subject must be SMALLINT, INTEGER, BIGINT, REAL, or DOUBLE PRECISION values")));
break;
}
PG_RETURN_ARRAYTYPE_P(retArray);
}