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#include "postgres.h"
#include "fmgr.h"
#include "windowapi.h"
PG_MODULE_MAGIC;
PG_FUNCTION_INFO_V1(window_lag_ignore_nulls);
PG_FUNCTION_INFO_V1(window_lag_ignore_nulls_with_offset);
PG_FUNCTION_INFO_V1(window_lag_ignore_nulls_with_offset_with_default);
PG_FUNCTION_INFO_V1(window_lead_ignore_nulls);
PG_FUNCTION_INFO_V1(window_lead_ignore_nulls_with_offset);
PG_FUNCTION_INFO_V1(window_lead_ignore_nulls_with_offset_with_default);
PG_FUNCTION_INFO_V1(window_first_value_ignore_nulls);
PG_FUNCTION_INFO_V1(window_first_value_ignore_nulls_with_default);
PG_FUNCTION_INFO_V1(window_last_value_ignore_nulls);
PG_FUNCTION_INFO_V1(window_last_value_ignore_nulls_with_default);
PG_FUNCTION_INFO_V1(window_nth_value_from_last);
PG_FUNCTION_INFO_V1(window_nth_value_from_last_ignore_nulls);
PG_FUNCTION_INFO_V1(window_nth_value_from_last_ignore_nulls_with_default);
PG_FUNCTION_INFO_V1(window_nth_value_from_last_with_default);
PG_FUNCTION_INFO_V1(window_nth_value_ignore_nulls);
PG_FUNCTION_INFO_V1(window_nth_value_ignore_nulls_with_default);
PG_FUNCTION_INFO_V1(window_nth_value_with_default);
PG_FUNCTION_INFO_V1(window_flip_flop_1);
PG_FUNCTION_INFO_V1(window_flip_flop_2);
typedef struct flip_flop_context
{
bool flip_flop;
} flip_flop_context;
/* LEAD / LAG COMMON */
static Datum
lead_lag_common(
FunctionCallInfo fcinfo,
bool forward, bool with_offset, bool with_default)
{
WindowObject winobj = PG_WINDOW_OBJECT();
int32 offset;
/*bool const_offset;*/
Datum result;
bool isnull;
bool isout;
int step = forward ? 1 : -1;
int runner = step;
if (with_offset)
{
offset = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
if (isnull)
PG_RETURN_NULL();
}
else
offset = 1;
if (!forward)
offset = -offset;
if (offset == 0)
runner = 0;
for (;;)
{
result = WinGetFuncArgInPartition(winobj, 0,
runner,
WINDOW_SEEK_CURRENT,
false,
&isnull, &isout);
if (isout)
break;
if (isnull)
offset += step;
if (runner == offset)
break;
runner += step;
}
if (isout)
{
/*
* target row is out of the partition; supply default value if
* provided. otherwise it'll stay NULL
*/
if (with_default)
result = WinGetFuncArgCurrent(winobj, 2, &isnull);
}
if (isnull)
PG_RETURN_NULL();
PG_RETURN_DATUM(result);
}
Datum
window_lag_ignore_nulls(PG_FUNCTION_ARGS)
{
return lead_lag_common(fcinfo, false, false, false);
}
Datum
window_lag_ignore_nulls_with_offset(PG_FUNCTION_ARGS)
{
return lead_lag_common(fcinfo, false, true, false);
}
Datum
window_lag_ignore_nulls_with_offset_with_default(PG_FUNCTION_ARGS)
{
return lead_lag_common(fcinfo, false, true, true);
}
Datum
window_lead_ignore_nulls(PG_FUNCTION_ARGS)
{
return lead_lag_common(fcinfo, true, false, false);
}
Datum
window_lead_ignore_nulls_with_offset(PG_FUNCTION_ARGS)
{
return lead_lag_common(fcinfo, true, true, false);
}
Datum
window_lead_ignore_nulls_with_offset_with_default(PG_FUNCTION_ARGS)
{
return lead_lag_common(fcinfo, true, true, true);
}
/* FIRST_VALUE / LAST_VALUE COMMON */
static Datum
first_last_value_common(
FunctionCallInfo fcinfo,
bool from_last, bool with_default)
{
WindowObject winobj = PG_WINDOW_OBJECT();
Datum result;
bool isnull;
bool isout;
int runner = 0;
int step = from_last ? -1 : 1;
for (;;)
{
result = WinGetFuncArgInFrame(
winobj, 0, runner,
from_last ? WINDOW_SEEK_TAIL : WINDOW_SEEK_HEAD,
false, &isnull, &isout);
if (isout || !isnull)
break;
runner += step;
}
if (isout && with_default)
result = WinGetFuncArgCurrent(winobj, 1, &isnull);
if (isnull)
PG_RETURN_NULL();
PG_RETURN_DATUM(result);
}
/* FIRST_VALUE */
Datum
window_first_value_ignore_nulls(PG_FUNCTION_ARGS)
{
return first_last_value_common(fcinfo, false, false);
}
Datum
window_first_value_ignore_nulls_with_default(PG_FUNCTION_ARGS)
{
return first_last_value_common(fcinfo, false, true);
}
/* LAST_VALUE */
Datum
window_last_value_ignore_nulls(PG_FUNCTION_ARGS)
{
return first_last_value_common(fcinfo, true, false);
}
Datum
window_last_value_ignore_nulls_with_default(PG_FUNCTION_ARGS)
{
return first_last_value_common(fcinfo, true, true);
}
/* NTH_VALUE COMMON */
static Datum
nth_value_common(
FunctionCallInfo fcinfo, const char *fname,
bool from_last, bool ignore_nulls, bool with_default)
{
WindowObject winobj = PG_WINDOW_OBJECT();
Datum result;
bool isnull;
bool isout;
int32 nth;
int seektype;
nth = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull)) - 1;
if (isnull)
PG_RETURN_NULL();
if (nth < 0)
ereport(ERROR,
(errcode(ERRCODE_INVALID_ARGUMENT_FOR_NTH_VALUE),
errmsg("argument of %s must be greater than zero", fname)));
if (from_last)
{
seektype = WINDOW_SEEK_TAIL;
nth = -nth;
}
else
seektype = WINDOW_SEEK_HEAD;
if (ignore_nulls)
{
int runner = 0;
int step = from_last ? -1 : 1;
for (;;)
{
result = WinGetFuncArgInFrame(winobj, 0,
runner, seektype, false,
&isnull, &isout);
if (isout)
break;
if (isnull)
nth += step;
if (runner == nth)
break;
runner += step;
}
}
else
{
bool const_offset = get_fn_expr_arg_stable(fcinfo->flinfo, 1);
result = WinGetFuncArgInFrame(winobj, 0,
nth, seektype, const_offset,
&isnull, &isout);
}
if (isout && with_default)
result = WinGetFuncArgCurrent(winobj, 2, &isnull);
if (isnull)
PG_RETURN_NULL();
PG_RETURN_DATUM(result);
}
/* NTH_VALUE */
Datum
window_nth_value_from_last(PG_FUNCTION_ARGS)
{
return nth_value_common(fcinfo, "nth_value_from_last", true, false, false);
}
Datum
window_nth_value_from_last_ignore_nulls(PG_FUNCTION_ARGS)
{
return nth_value_common(fcinfo, "nth_value_from_last_ignore_nulls", true, true, false);
}
Datum
window_nth_value_from_last_ignore_nulls_with_default(PG_FUNCTION_ARGS)
{
return nth_value_common(fcinfo, "nth_value_from_last_ignore_nulls", true, true, true);
}
Datum
window_nth_value_from_last_with_default(PG_FUNCTION_ARGS)
{
return nth_value_common(fcinfo, "nth_value_from_last", true, false, true);
}
Datum
window_nth_value_ignore_nulls(PG_FUNCTION_ARGS)
{
return nth_value_common(fcinfo, "nth_value_ignore_nulls", false, true, false);
}
Datum
window_nth_value_ignore_nulls_with_default(PG_FUNCTION_ARGS)
{
return nth_value_common(fcinfo, "nth_value_ignore_nulls", false, true, true);
}
Datum
window_nth_value_with_default(PG_FUNCTION_ARGS)
{
return nth_value_common(fcinfo, "nth_value", false, false, true);
}
/* FLIP_FLOP */
static Datum
flip_flop(FunctionCallInfo fcinfo, int flip_argno, int flop_argno)
{
WindowObject winobj = PG_WINDOW_OBJECT();
flip_flop_context *context;
bool isnull;
context = (flip_flop_context *)
WinGetPartitionLocalMemory(winobj, sizeof(flip_flop_context));
if (!context->flip_flop)
{
bool flip;
flip = WinGetFuncArgCurrent(winobj, flip_argno, &isnull);
if (!isnull && flip)
{
context->flip_flop = true;
PG_RETURN_BOOL(true);
}
PG_RETURN_BOOL(false);
}
else
{
bool flop;
flop = WinGetFuncArgCurrent(winobj, flop_argno, &isnull);
if (!isnull && flop)
context->flip_flop = false;
PG_RETURN_BOOL(true);
}
}
Datum
window_flip_flop_1(PG_FUNCTION_ARGS)
{
return flip_flop(fcinfo, 0, 0);
}
Datum
window_flip_flop_2(PG_FUNCTION_ARGS)
{
return flip_flop(fcinfo, 0, 1);
}
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