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array_median.c
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array_median.c
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/*
array_median.c
#### replace to your local include dir, c file, so file, o file.
gcc -I/home/jian/postgres/2023_05_25_beta5421/include/server -fPIC -c /home/jian/Desktop/regress_pgsql/array_median.c
gcc -shared -o /home/jian/Desktop/regress_pgsql/array_median.so /home/jian/Desktop/regress_pgsql/array_median.o
get median of an unsorted array, now only support non-null array.
base type can be {int2, int4, int8, date, interval, numeric, timestamp, timestamptz}
* http://ndevilla.free.fr/median/median/src/quickselect.c
* This Quickselect routine is based on the algorithm described in
* "Numerical recipes in C", Second Edition,
* Cambridge University Press, 1992, Section 8.5, ISBN 0-521-43108-5
* This code by Nicolas Devillard - 1998. Public domain.
*
*/
#include "postgres.h"
#include "utils/builtins.h"
#include "utils/array.h"
#include "utils/numeric.h"
#include "utils/datetime.h"
#include "utils/date.h"
#include "utils/timestamp.h"
#include "utils/timeout.h"
#include "utils/pg_lsn.h"
#include "funcapi.h"
#include "utils/lsyscache.h"
#include "utils/fmgrprotos.h"
PG_MODULE_MAGIC;
PG_FUNCTION_INFO_V1(array_median);
#define ELEM_SWAP(a,b) do { register int t=(a);(a)=(b);(b)=t; } while(0)
#define swapDatum(a,b) do {Datum _tmp; _tmp=a; a=b; b=_tmp;} while(0)
Datum
array_median(PG_FUNCTION_ARGS)
{
ArrayType *arr;
ArrayType *arr_copy;
Datum *type_oids;
Oid basetype;
int nelements;
int16 typlen;
bool typbyval;
char typalign;
bool *typnullflag;
int i;
bool resisnull = true;
Datum temp;
Datum temp1;
int nullcnt = 0; /* init value for later doing arithmetic */
int non_nullcnt;
if (PG_ARGISNULL(0))
PG_RETURN_NULL();
arr = PG_GETARG_ARRAYTYPE_P_COPY(0);
//todo use array_remove to alloq array contain null
if (ARR_HASNULL(arr) && array_contains_nulls(arr))
elog(ERROR,"%s argument must not contain nulls",__func__);
// This requirement could probably be lifted pretty easily:
if (ARR_NDIM(arr) != 1)
ereport(ERROR, (errmsg("One-dimesional arrays are required")));
//actual data pointer.
type_oids = (Datum *) ARR_DATA_PTR(arr);
basetype = ARR_ELEMTYPE(arr);
get_typlenbyvalalign(basetype, &typlen, &typbyval, &typalign);
nelements = ArrayGetNItems(ARR_NDIM(arr), ARR_DIMS(arr));
// Extract the array contents (as Datum objects).
deconstruct_array(arr,basetype,typlen,typbyval,typalign,&type_oids,&typnullflag,&nelements);
int low = 0;
int high = nelements - 1;
int median = (low + high) / 2;
int middle,ll, hh;
temp = type_oids[0];
switch (basetype)
{
case INT2OID:
for (;;)
{
if (high <= low) /* One element only */
PG_RETURN_DATUM(type_oids[median]);
if (high == low + 1) /* Two elements only */
{
if ( (bool) DirectFunctionCall2(int2gt,type_oids[low],type_oids[high]) )
swapDatum(type_oids[low], type_oids[high]);
PG_RETURN_DATUM(type_oids[median]);
}
/* Find median of low, middle and high items; swap into position low */
middle = (low + high) / 2;
if ( (bool) DirectFunctionCall2(int2gt,type_oids[middle], type_oids[high]) )
swapDatum(type_oids[middle], type_oids[high]);
if ( (bool) DirectFunctionCall2(int2gt,type_oids[low], type_oids[high]) )
swapDatum(type_oids[low], type_oids[high]);
if ( (bool) DirectFunctionCall2(int2gt,type_oids[middle], type_oids[low]) )
swapDatum(type_oids[middle], type_oids[low]);
/* Swap low item (now in position middle) into position (low+1) */
swapDatum(type_oids[middle], type_oids[low+1]);
/* Nibble from each end towards middle, swapping items when stuck */
ll = low + 1;
hh = high;
for (;;)
{
do ll++;
while ((bool) DirectFunctionCall2(int2gt,type_oids[low], type_oids[ll])) ;
do hh--;
while ((bool) DirectFunctionCall2(int2gt,type_oids[hh], type_oids[low])) ;
if (hh < ll)
break;
swapDatum(type_oids[ll], type_oids[hh]);
}
/* Swap middle item (in position low) back into correct position */
swapDatum(type_oids[low], type_oids[hh]);
/* Re-set active partition */
if (hh <= median)
low = ll;
if (hh >= median)
high = hh - 1;
}
case INT4OID:
for (;;)
{
if (high <= low) /* One element only */
PG_RETURN_DATUM(type_oids[median]);
if (high == low + 1) /* Two elements only */
{
if ( (bool) DirectFunctionCall2(int4gt,type_oids[low],type_oids[high]) )
swapDatum(type_oids[low], type_oids[high]);
PG_RETURN_DATUM(type_oids[median]);
}
/* Find median of low, middle and high items; swap into position low */
middle = (low + high) / 2;
if ( (bool) DirectFunctionCall2(int4gt,type_oids[middle], type_oids[high]) )
swapDatum(type_oids[middle], type_oids[high]);
if ( (bool) DirectFunctionCall2(int4gt,type_oids[low], type_oids[high]) )
swapDatum(type_oids[low], type_oids[high]);
if ( (bool) DirectFunctionCall2(int4gt,type_oids[middle], type_oids[low]) )
swapDatum(type_oids[middle], type_oids[low]);
/* Swap low item (now in position middle) into position (low+1) */
swapDatum(type_oids[middle], type_oids[low+1]);
/* Nibble from each end towards middle, swapping items when stuck */
ll = low + 1;
hh = high;
for (;;)
{
do ll++;
while ((bool) DirectFunctionCall2(int4gt,type_oids[low], type_oids[ll])) ;
do hh--;
while ((bool) DirectFunctionCall2(int4gt,type_oids[hh], type_oids[low])) ;
if (hh < ll)
break;
swapDatum(type_oids[ll], type_oids[hh]);
}
/* Swap middle item (in position low) back into correct position */
swapDatum(type_oids[low], type_oids[hh]);
/* Re-set active partition */
if (hh <= median)
low = ll;
if (hh >= median)
high = hh - 1;
}
case INT8OID:
for (;;)
{
if (high <= low) /* One element only */
PG_RETURN_DATUM(type_oids[median]);
if (high == low + 1) /* Two elements only */
{
if ( (bool) DirectFunctionCall2(int8gt,type_oids[low],type_oids[high]) )
swapDatum(type_oids[low], type_oids[high]);
PG_RETURN_DATUM(type_oids[median]);
}
/* Find median of low, middle and high items; swap into position low */
middle = (low + high) / 2;
if ( (bool) DirectFunctionCall2(int8gt,type_oids[middle], type_oids[high]) )
swapDatum(type_oids[middle], type_oids[high]);
if ( (bool) DirectFunctionCall2(int8gt,type_oids[low], type_oids[high]) )
swapDatum(type_oids[low], type_oids[high]);
if ( (bool) DirectFunctionCall2(int8gt,type_oids[middle], type_oids[low]) )
swapDatum(type_oids[middle], type_oids[low]);
/* Swap low item (now in position middle) into position (low+1) */
swapDatum(type_oids[middle], type_oids[low+1]);
/* Nibble from each end towards middle, swapping items when stuck */
ll = low + 1;
hh = high;
for (;;)
{
do ll++;
while ((bool) DirectFunctionCall2(int8gt,type_oids[low], type_oids[ll])) ;
do hh--;
while ((bool) DirectFunctionCall2(int8gt,type_oids[hh], type_oids[low])) ;
if (hh < ll)
break;
swapDatum(type_oids[ll], type_oids[hh]);
}
/* Swap middle item (in position low) back into correct position */
swapDatum(type_oids[low], type_oids[hh]);
/* Re-set active partition */
if (hh <= median)
low = ll;
if (hh >= median)
high = hh - 1;
}
case DATEOID:
for (;;)
{
if (high <= low) /* One element only */
PG_RETURN_DATUM(type_oids[median]);
if (high == low + 1) /* Two elements only */
{
if ( (bool) DirectFunctionCall2(date_gt,type_oids[low],type_oids[high]) )
swapDatum(type_oids[low], type_oids[high]);
PG_RETURN_DATUM(type_oids[median]);
}
/* Find median of low, middle and high items; swap into position low */
middle = (low + high) / 2;
if ( (bool) DirectFunctionCall2(date_gt,type_oids[middle], type_oids[high]) )
swapDatum(type_oids[middle], type_oids[high]);
if ( (bool) DirectFunctionCall2(date_gt,type_oids[low], type_oids[high]) )
swapDatum(type_oids[low], type_oids[high]);
if ( (bool) DirectFunctionCall2(date_gt,type_oids[middle], type_oids[low]) )
swapDatum(type_oids[middle], type_oids[low]);
/* Swap low item (now in position middle) into position (low+1) */
swapDatum(type_oids[middle], type_oids[low+1]);
/* Nibble from each end towards middle, swapping items when stuck */
ll = low + 1;
hh = high;
for (;;)
{
do ll++;
while ((bool) DirectFunctionCall2(date_gt,type_oids[low], type_oids[ll])) ;
do hh--;
while ((bool) DirectFunctionCall2(date_gt,type_oids[hh], type_oids[low])) ;
if (hh < ll)
break;
swapDatum(type_oids[ll], type_oids[hh]);
}
/* Swap middle item (in position low) back into correct position */
swapDatum(type_oids[low], type_oids[hh]);
/* Re-set active partition */
if (hh <= median)
low = ll;
if (hh >= median)
high = hh - 1;
}
case TIMESTAMPOID:
for (;;)
{
if (high <= low) /* One element only */
PG_RETURN_DATUM(type_oids[median]);
if (high == low + 1) /* Two elements only */
{
if ( (bool) DirectFunctionCall2(timestamp_gt,type_oids[low],type_oids[high]) )
swapDatum(type_oids[low], type_oids[high]);
PG_RETURN_DATUM(type_oids[median]);
}
/* Find median of low, middle and high items; swap into position low */
middle = (low + high) / 2;
if ( (bool) DirectFunctionCall2(timestamp_gt,type_oids[middle], type_oids[high]) )
swapDatum(type_oids[middle], type_oids[high]);
if ( (bool) DirectFunctionCall2(timestamp_gt,type_oids[low], type_oids[high]) )
swapDatum(type_oids[low], type_oids[high]);
if ( (bool) DirectFunctionCall2(timestamp_gt,type_oids[middle], type_oids[low]) )
swapDatum(type_oids[middle], type_oids[low]);
/* Swap low item (now in position middle) into position (low+1) */
swapDatum(type_oids[middle], type_oids[low+1]);
/* Nibble from each end towards middle, swapping items when stuck */
ll = low + 1;
hh = high;
for (;;)
{
do ll++;
while ((bool) DirectFunctionCall2(timestamp_gt,type_oids[low], type_oids[ll])) ;
do hh--;
while ((bool) DirectFunctionCall2(timestamp_gt,type_oids[hh], type_oids[low])) ;
if (hh < ll)
break;
swapDatum(type_oids[ll], type_oids[hh]);
}
/* Swap middle item (in position low) back into correct position */
swapDatum(type_oids[low], type_oids[hh]);
/* Re-set active partition */
if (hh <= median)
low = ll;
if (hh >= median)
high = hh - 1;
}
case TIMESTAMPTZOID:
for (;;)
{
if (high <= low) /* One element only */
PG_RETURN_DATUM(type_oids[median]);
if (high == low + 1) /* Two elements only */
{
if ( (bool) DirectFunctionCall2(timestamptz_gt_timestamp,type_oids[low],type_oids[high]) )
swapDatum(type_oids[low], type_oids[high]);
PG_RETURN_DATUM(type_oids[median]);
}
/* Find median of low, middle and high items; swap into position low */
middle = (low + high) / 2;
if ( (bool) DirectFunctionCall2(timestamptz_gt_timestamp,type_oids[middle], type_oids[high]) )
swapDatum(type_oids[middle], type_oids[high]);
if ( (bool) DirectFunctionCall2(timestamptz_gt_timestamp,type_oids[low], type_oids[high]) )
swapDatum(type_oids[low], type_oids[high]);
if ( (bool) DirectFunctionCall2(timestamptz_gt_timestamp,type_oids[middle], type_oids[low]) )
swapDatum(type_oids[middle], type_oids[low]);
/* Swap low item (now in position middle) into position (low+1) */
swapDatum(type_oids[middle], type_oids[low+1]);
/* Nibble from each end towards middle, swapping items when stuck */
ll = low + 1;
hh = high;
for (;;)
{
do ll++;
while ((bool) DirectFunctionCall2(timestamptz_gt_timestamp,type_oids[low], type_oids[ll])) ;
do hh--;
while ((bool) DirectFunctionCall2(timestamptz_gt_timestamp,type_oids[hh], type_oids[low])) ;
if (hh < ll)
break;
swapDatum(type_oids[ll], type_oids[hh]);
}
/* Swap middle item (in position low) back into correct position */
swapDatum(type_oids[low], type_oids[hh]);
/* Re-set active partition */
if (hh <= median)
low = ll;
if (hh >= median)
high = hh - 1;
}
case INTERVALOID:
for (;;)
{
if (high <= low) /* One element only */
PG_RETURN_DATUM(type_oids[median]);
if (high == low + 1) /* Two elements only */
{
if ( (bool) DirectFunctionCall2(interval_gt,type_oids[low],type_oids[high]) )
swapDatum(type_oids[low], type_oids[high]);
PG_RETURN_DATUM(type_oids[median]);
}
/* Find median of low, middle and high items; swap into position low */
middle = (low + high) / 2;
if ( (bool) DirectFunctionCall2(interval_gt,type_oids[middle], type_oids[high]) )
swapDatum(type_oids[middle], type_oids[high]);
if ( (bool) DirectFunctionCall2(interval_gt,type_oids[low], type_oids[high]) )
swapDatum(type_oids[low], type_oids[high]);
if ( (bool) DirectFunctionCall2(interval_gt,type_oids[middle], type_oids[low]) )
swapDatum(type_oids[middle], type_oids[low]);
/* Swap low item (now in position middle) into position (low+1) */
swapDatum(type_oids[middle], type_oids[low+1]);
/* Nibble from each end towards middle, swapping items when stuck */
ll = low + 1;
hh = high;
for (;;)
{
do ll++;
while ((bool) DirectFunctionCall2(interval_gt,type_oids[low], type_oids[ll])) ;
do hh--;
while ((bool) DirectFunctionCall2(interval_gt,type_oids[hh], type_oids[low])) ;
if (hh < ll)
break;
swapDatum(type_oids[ll], type_oids[hh]);
}
/* Swap middle item (in position low) back into correct position */
swapDatum(type_oids[low], type_oids[hh]);
/* Re-set active partition */
if (hh <= median)
low = ll;
if (hh >= median)
high = hh - 1;
}
case NUMERICOID:
for (;;)
{
if (high <= low) /* One element only */
PG_RETURN_DATUM(type_oids[median]);
if (high == low + 1) /* Two elements only */
{
if ( (bool) DirectFunctionCall2(numeric_gt,type_oids[low],type_oids[high]) )
swapDatum(type_oids[low], type_oids[high]);
PG_RETURN_DATUM(type_oids[median]);
}
/* Find median of low, middle and high items; swap into position low */
middle = (low + high) / 2;
if ( (bool) DirectFunctionCall2(numeric_gt,type_oids[middle], type_oids[high]) )
swapDatum(type_oids[middle], type_oids[high]);
if ( (bool) DirectFunctionCall2(numeric_gt,type_oids[low], type_oids[high]) )
swapDatum(type_oids[low], type_oids[high]);
if ( (bool) DirectFunctionCall2(numeric_gt,type_oids[middle], type_oids[low]) )
swapDatum(type_oids[middle], type_oids[low]);
/* Swap low item (now in position middle) into position (low+1) */
swapDatum(type_oids[middle], type_oids[low+1]);
/* Nibble from each end towards middle, swapping items when stuck */
ll = low + 1;
hh = high;
for (;;)
{
do ll++;
while ((bool) DirectFunctionCall2(numeric_gt,type_oids[low], type_oids[ll])) ;
do hh--;
while ((bool) DirectFunctionCall2(numeric_gt,type_oids[hh], type_oids[low])) ;
if (hh < ll)
break;
swapDatum(type_oids[ll], type_oids[hh]);
}
/* Swap middle item (in position low) back into correct position */
swapDatum(type_oids[low], type_oids[hh]);
/* Re-set active partition */
if (hh <= median)
low = ll;
if (hh >= median)
high = hh - 1;
}
default:
ereport(ERROR, (errmsg("allowed data type int2, int4, int8, float4, float8, numeric")));
}
}