Changeset: 84ff15371e4d for MonetDB
URL: https://dev.monetdb.org/hg/MonetDB?cmd=changeset;node=84ff15371e4d
Modified Files:
gdk/gdk_hash.h
Branch: linear-hashing
Log Message:
Update comments.
diffs (36 lines):
diff --git a/gdk/gdk_hash.h b/gdk/gdk_hash.h
--- a/gdk/gdk_hash.h
+++ b/gdk/gdk_hash.h
@@ -9,28 +9,17 @@
#ifndef _GDK_SEARCH_H_
#define _GDK_SEARCH_H_
-/*
- * @+ Hash indexing
- *
- * This is a highly efficient implementation of simple bucket-chained
- * hashing.
- *
- * In the past, we used integer modulo for hashing, with bucket chains
- * of mean size 4. This was shown to be inferior to direct hashing
- * with integer anding. The new implementation reflects this.
- */
-
typedef struct Hash {
int type; /* type of index entity */
uint8_t width; /* width of hash entries */
BUN mask1; /* .mask1 < .nbucket <= .mask2 */
- BUN mask2;
- BUN nbucket; /* ... depending on hash value and .nbucket */
+ BUN mask2; /* ... both are power-of-two minus one */
+ BUN nbucket; /* number of valid hash buckets */
BUN nil; /* nil representation */
BUN nunique; /* number of unique values */
BUN nheads; /* number of chain heads */
- void *Bckt; /* hash buckets */
- void *Link; /* collision list */
+ void *Bckt; /* hash buckets, points into .heapbckt */
+ void *Link; /* collision list, points into .heaplink */
Heap heaplink; /* heap where the hash links are stored */
Heap heapbckt; /* heap where the hash buckets are stored */
} Hash;
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