Add pairingheap_initialize() for shared memory usage

The existing pairingheap_allocate() uses palloc(), which allocates
from process-local memory. For shared memory use cases, the pairingheap
structure must be allocated via ShmemAlloc() or embedded in a shared
memory struct. Add pairingheap_initialize() to initialize an already-
allocated pairingheap structure in-place, enabling shared memory usage.

Discussion: https://www.postgresql.org/message-id/flat/CAPpHfdsjtZLVzxjGT8rJHCYbM0D5dwkO+BBjcirozJ6nYbOW8Q@mail.gmail.com
Discussion: https://www.postgresql.org/message-id/flat/CABPTF7UNft368x-RgOXkfj475OwEbp%2BVVO-wEXz7StgjD_%3D6sw%40mail.gmail.com
Author: Kartyshov Ivan <i.kartyshov@postgrespro.ru>
Author: Alexander Korotkov <aekorotkov@gmail.com>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Reviewed-by: Peter Eisentraut <peter.eisentraut@enterprisedb.com>
Reviewed-by: Dilip Kumar <dilipbalaut@gmail.com>
Reviewed-by: Amit Kapila <amit.kapila16@gmail.com>
Reviewed-by: Alexander Lakhin <exclusion@gmail.com>
Reviewed-by: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Reviewed-by: Euler Taveira <euler@eulerto.com>
Reviewed-by: Heikki Linnakangas <hlinnaka@iki.fi>
Reviewed-by: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Reviewed-by: Xuneng Zhou <xunengzhou@gmail.com>

diff --git a/src/backend/lib/pairingheap.c b/src/backend/lib/pairingheap.c
index 0aef8a88f1b5ec64d736ba8b99279986e40de083..fa8431f794639df76f87255b56b3552f8e25a688 100644 (file)
--- a/src/backend/lib/pairingheap.c
+++ b/src/backend/lib/pairingheap.c
@@ -44,12 +44,26 @@ pairingheap_allocate(pairingheap_comparator compare, void *arg)
        pairingheap *heap;
 
        heap = (pairingheap *) palloc(sizeof(pairingheap));
+       pairingheap_initialize(heap, compare, arg);
+
+       return heap;
+}
+
+/*
+ * pairingheap_initialize
+ *
+ * Same as pairingheap_allocate(), but initializes the pairing heap in-place
+ * rather than allocating a new chunk of memory.  Useful to store the pairing
+ * heap in a shared memory.
+ */
+void
+pairingheap_initialize(pairingheap *heap, pairingheap_comparator compare,
+                                          void *arg)
+{
        heap->ph_compare = compare;
        heap->ph_arg = arg;
 
        heap->ph_root = NULL;
-
-       return heap;
 }
 
 /*

diff --git a/src/include/lib/pairingheap.h b/src/include/lib/pairingheap.h
index 3c57d3fda1bbecf3e4742f2acecc34cfd164e015..567586f2ecf9c5cf86ab935ddbc1c7f056e335cd 100644 (file)
--- a/src/include/lib/pairingheap.h
+++ b/src/include/lib/pairingheap.h
@@ -77,6 +77,9 @@ typedef struct pairingheap
 
 extern pairingheap *pairingheap_allocate(pairingheap_comparator compare,
                                                                                 void *arg);
+extern void pairingheap_initialize(pairingheap *heap,
+                                                                  pairingheap_comparator compare,
+                                                                  void *arg);
 extern void pairingheap_free(pairingheap *heap);
 extern void pairingheap_add(pairingheap *heap, pairingheap_node *node);
 extern pairingheap_node *pairingheap_first(pairingheap *heap);