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Support for unnest(multirange)

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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), which is quite trivial.
unnest(multirange) is defined as a polymorphic procedure.

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, Tom Lane
Reviewed-by: Alvaro Herrera
This commit is contained in:
Alexander Korotkov
2021-07-18 21:07:24 +03:00
parent ba620760c4
commit 9e3c217bd9
5 changed files with 131 additions and 0 deletions
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73
src/backend/utils/adt/multirangetypes.c
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@@ -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"
@@ -2645,6 +2646,78 @@ 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 */