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Support for unnest(multirange) and cast multirange as an array of ranges

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It has been spotted that multiranges lack of ability to decompose them into
individual ranges.  Subscription and proper expanded object representation
require substantial work, and it's too late for v14.  This commit
provides the implementation of unnest(multirange) and cast multirange as
an array of ranges, which is quite trivial.

unnest(multirange) is defined as a polymorphic procedure.  The catalog
description of the cast underlying procedure is duplicated for each multirange
type because we don't have anyrangearray polymorphic type to use here.

Catversion is bumped.

Reported-by: Jonathan S. Katz
Discussion: https://postgr.es/m/flat/60258efe-bd7e-4886-82e1-196e0cac5433%40postgresql.org
Author: Alexander Korotkov
Reviewed-by: Justin Pryzby, Jonathan S. Katz, Zhihong Yu
This commit is contained in:
Alexander Korotkov
2021-06-15 15:59:20 +03:00
parent 4daa140a2f
commit 29854ee8d1
11 changed files with 354 additions and 9 deletions
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106
src/backend/utils/adt/multirangetypes.c
View File

@@ -34,6 +34,7 @@
#include "access/tupmacs.h"
#include "common/hashfn.h"
#include "funcapi.h"
#include "lib/stringinfo.h"
#include "libpq/pqformat.h"
#include "miscadmin.h"
@@ -1068,6 +1069,39 @@ multirange_constructor0(PG_FUNCTION_ARGS)
PG_RETURN_MULTIRANGE_P(make_multirange(mltrngtypid, rangetyp, 0, NULL));
}
/*
* Cast multirange to an array of ranges.
*/
Datum
multirange_to_array(PG_FUNCTION_ARGS)
{
ArrayBuildState *astate = NULL;
MultirangeType *mr = PG_GETARG_MULTIRANGE_P(0);
TypeCacheEntry *typcache;
int i;
typcache = multirange_get_typcache(fcinfo, MultirangeTypeGetOid(mr));
astate = initArrayResult(typcache->rngtype->type_id,
CurrentMemoryContext,
false);
for (i = 0; i < mr->rangeCount; i++)
{
RangeType *r;
r = multirange_get_range(typcache->rngtype, mr, i);
astate = accumArrayResult(astate,
RangeTypePGetDatum(r),
false,
typcache->rngtype->type_id,
CurrentMemoryContext);
}
PG_RETURN_ARRAYTYPE_P(makeArrayResult(astate, CurrentMemoryContext));
}
/* multirange, multirange -> multirange type functions */
@@ -2645,6 +2679,78 @@ range_merge_from_multirange(PG_FUNCTION_ARGS)
PG_RETURN_RANGE_P(result);
}
/* Turn multirange into a set of ranges */
Datum
multirange_unnest(PG_FUNCTION_ARGS)
{
typedef struct
{
MultirangeType *mr;
TypeCacheEntry *typcache;
int index;
} multirange_unnest_fctx;
FuncCallContext *funcctx;
multirange_unnest_fctx *fctx;
MemoryContext oldcontext;
/* stuff done only on the first call of the function */
if (SRF_IS_FIRSTCALL())
{
MultirangeType *mr;
/* create a function context for cross-call persistence */
funcctx = SRF_FIRSTCALL_INIT();
/*
* switch to memory context appropriate for multiple function calls
*/
oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
/*
* Get the multirange value and detoast if needed. We can't do this
* earlier because if we have to detoast, we want the detoasted copy
* to be in multi_call_memory_ctx, so it will go away when we're done
* and not before. (If no detoast happens, we assume the originally
* passed multirange will stick around till then.)
*/
mr = PG_GETARG_MULTIRANGE_P(0);
/* allocate memory for user context */
fctx = (multirange_unnest_fctx *) palloc(sizeof(multirange_unnest_fctx));
/* initialize state */
fctx->mr = mr;
fctx->index = 0;
fctx->typcache = lookup_type_cache(MultirangeTypeGetOid(mr),
TYPECACHE_MULTIRANGE_INFO);
funcctx->user_fctx = fctx;
MemoryContextSwitchTo(oldcontext);
}
/* stuff done on every call of the function */
funcctx = SRF_PERCALL_SETUP();
fctx = funcctx->user_fctx;
if (fctx->index < fctx->mr->rangeCount)
{
RangeType *range;
range = multirange_get_range(fctx->typcache->rngtype,
fctx->mr,
fctx->index);
fctx->index++;
SRF_RETURN_NEXT(funcctx, RangeTypePGetDatum(range));
}
else
{
/* do when there is no more left */
SRF_RETURN_DONE(funcctx);
}
}
/* Hash support */
/* hash a multirange value */