From 565903af474e85cef28ff712d773f13b6701ded5 Mon Sep 17 00:00:00 2001
From: Robert Haas <rhaas@postgresql.org>
Date: Tue, 7 Feb 2017 15:58:30 -0500
Subject: [PATCH] Allow the element allocator for a simplehash to be specified.
This is infrastructure for a pending patch to allow parallel bitmap
heap scans.
Dilip Kumar, reviewed (in earlier versions) by Andres Freund and
(more recently) by me. Some further renaming by me, also.
---
src/backend/executor/execGrouping.c | 3 +-
src/backend/nodes/tidbitmap.c | 2 +-
src/include/lib/simplehash.h | 69 ++++++++++++++++++++++++-----
3 files changed, 60 insertions(+), 14 deletions(-)
diff --git a/src/backend/executor/execGrouping.c b/src/backend/executor/execGrouping.c
index 47c9656e1be..2d9ce938baf 100644
--- a/src/backend/executor/execGrouping.c
+++ b/src/backend/executor/execGrouping.c
@@ -330,7 +330,8 @@ BuildTupleHashTable(int numCols, AttrNumber *keyColIdx,
else
hashtable->hash_iv = 0;
- hashtable->hashtab = tuplehash_create(tablecxt, nbuckets);
+ hashtable->hashtab =
+ tuplehash_create(tablecxt, nbuckets, NULL, NULL, NULL);
hashtable->hashtab->private_data = hashtable;
return hashtable;
diff --git a/src/backend/nodes/tidbitmap.c b/src/backend/nodes/tidbitmap.c
index 7b31948fd28..36102b5deab 100644
--- a/src/backend/nodes/tidbitmap.c
+++ b/src/backend/nodes/tidbitmap.c
@@ -244,7 +244,7 @@ tbm_create_pagetable(TIDBitmap *tbm)
Assert(tbm->status != TBM_HASH);
Assert(tbm->pagetable == NULL);
- tbm->pagetable = pagetable_create(tbm->mcxt, 128);
+ tbm->pagetable = pagetable_create(tbm->mcxt, 128, NULL, NULL, NULL);
/* If entry1 is valid, push it into the hashtable */
if (tbm->status == TBM_ONE_PAGE)
diff --git a/src/include/lib/simplehash.h b/src/include/lib/simplehash.h
index 72e18499c07..fd7063c216f 100644
--- a/src/include/lib/simplehash.h
+++ b/src/include/lib/simplehash.h
@@ -87,6 +87,10 @@
#define SH_INITIAL_BUCKET SH_MAKE_NAME(initial_bucket)
#define SH_ENTRY_HASH SH_MAKE_NAME(entry_hash)
+/* Allocation function for hash table elements */
+typedef void *(*simplehash_allocate) (Size size, void *args);
+typedef void (*simplehash_free) (void *pointer, void *args);
+
/* generate forward declarations necessary to use the hash table */
#ifdef SH_DECLARE
@@ -112,6 +116,11 @@ typedef struct SH_TYPE
/* hash buckets */
SH_ELEMENT_TYPE *data;
+ /* Allocation and free functions, and the associated context. */
+ simplehash_allocate element_alloc;
+ simplehash_free element_free;
+ void *element_args;
+
/* memory context to use for allocations */
MemoryContext ctx;
@@ -133,7 +142,8 @@ typedef struct SH_ITERATOR
} SH_ITERATOR;
/* externally visible function prototypes */
-SH_SCOPE SH_TYPE *SH_CREATE(MemoryContext ctx, uint32 nelements);
+SH_SCOPE SH_TYPE *SH_CREATE(MemoryContext ctx, uint32 nelements,
+ simplehash_allocate allocfunc, simplehash_free freefunc, void *args);
SH_SCOPE void SH_DESTROY(SH_TYPE *tb);
SH_SCOPE void SH_GROW(SH_TYPE *tb, uint32 newsize);
SH_SCOPE SH_ELEMENT_TYPE *SH_INSERT(SH_TYPE *tb, SH_KEY_TYPE key, bool *found);
@@ -276,12 +286,35 @@ SH_ENTRY_HASH(SH_TYPE *tb, SH_ELEMENT_TYPE * entry)
#endif
}
+/* default memory allocator function */
+static void *
+SH_DEFAULT_ALLOC(Size size, void *args)
+{
+ MemoryContext context = (MemoryContext) args;
+
+ return MemoryContextAllocExtended(context, size,
+ MCXT_ALLOC_HUGE | MCXT_ALLOC_ZERO);
+}
+
+/* default memory free function */
+static void
+SH_DEFAULT_FREE(void *pointer, void *args)
+{
+ pfree(pointer);
+}
+
/*
- * Create a hash table with enough space for `nelements` distinct members,
- * allocating required memory in the passed-in context.
+ * Create a hash table with enough space for `nelements` distinct members.
+ * Memory for the hash table is allocated from the passed-in context. If
+ * desired, the array of elements can be allocated using a passed-in allocator;
+ * this could be useful in order to place the array of elements in a shared
+ * memory, or in a context that will outlive the rest of the hash table.
+ * Memory other than for the array of elements will still be allocated from
+ * the passed-in context.
*/
SH_SCOPE SH_TYPE *
-SH_CREATE(MemoryContext ctx, uint32 nelements)
+SH_CREATE(MemoryContext ctx, uint32 nelements, simplehash_allocate allocfunc,
+ simplehash_free freefunc, void *args)
{
SH_TYPE *tb;
uint64 size;
@@ -294,9 +327,22 @@ SH_CREATE(MemoryContext ctx, uint32 nelements)
SH_COMPUTE_PARAMETERS(tb, size);
- tb->data = MemoryContextAllocExtended(tb->ctx,
- sizeof(SH_ELEMENT_TYPE) * tb->size,
- MCXT_ALLOC_HUGE | MCXT_ALLOC_ZERO);
+ if (allocfunc == NULL)
+ {
+ tb->element_alloc = SH_DEFAULT_ALLOC;
+ tb->element_free = SH_DEFAULT_FREE;
+ tb->element_args = ctx;
+ }
+ else
+ {
+ tb->element_alloc = allocfunc;
+ tb->element_free = freefunc;
+
+ tb->element_args = args;
+ }
+
+ tb->data = tb->element_alloc(sizeof(SH_ELEMENT_TYPE) * tb->size,
+ tb->element_args);
return tb;
}
@@ -305,7 +351,7 @@ SH_CREATE(MemoryContext ctx, uint32 nelements)
SH_SCOPE void
SH_DESTROY(SH_TYPE *tb)
{
- pfree(tb->data);
+ tb->element_free(tb->data, tb->element_args);
pfree(tb);
}
@@ -333,9 +379,8 @@ SH_GROW(SH_TYPE *tb, uint32 newsize)
/* compute parameters for new table */
SH_COMPUTE_PARAMETERS(tb, newsize);
- tb->data = MemoryContextAllocExtended(
- tb->ctx, sizeof(SH_ELEMENT_TYPE) * tb->size,
- MCXT_ALLOC_HUGE | MCXT_ALLOC_ZERO);
+ tb->data = tb->element_alloc(sizeof(SH_ELEMENT_TYPE) * tb->size,
+ tb->element_args);
newdata = tb->data;
@@ -421,7 +466,7 @@ SH_GROW(SH_TYPE *tb, uint32 newsize)
}
}
- pfree(olddata);
+ tb->element_free(olddata, tb->element_args);
}
/*
--
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