Changeset: 33fd055514de for MonetDB
URL: https://dev.monetdb.org/hg/MonetDB/rev/33fd055514de
Modified Files:
gdk/gdk_hash.c
gdk/gdk_private.h
gdk/gdk_utils.c
Branch: Jan2022
Log Message:
If the hash chain of the to-be-deleted value is longer than 1000, remove hash.
This fixes bug #7253.
diffs (62 lines):
diff --git a/gdk/gdk_hash.c b/gdk/gdk_hash.c
--- a/gdk/gdk_hash.c
+++ b/gdk/gdk_hash.c
@@ -1309,6 +1309,7 @@ HASHdelete_locked(BAT *b, BUN p, const v
return;
}
bool seen = false;
+ BUN links = 0;
for (;;) {
if (!seen)
seen = atomcmp(v, BUNtail(bi, hb)) == 0;
@@ -1323,6 +1324,12 @@ HASHdelete_locked(BAT *b, BUN p, const v
break;
}
hb = hb2;
+ if (++links > HASH_DESTROY_CHAIN_LENGTH) {
+ b->thash = NULL;
+ doHASHdestroy(b, h);
+ GDKclrerr();
+ return;
+ }
}
h->heaplink.dirty = true;
HASHputlink(h, hb, HASHgetlink(h, p));
diff --git a/gdk/gdk_private.h b/gdk/gdk_private.h
--- a/gdk/gdk_private.h
+++ b/gdk/gdk_private.h
@@ -476,6 +476,9 @@ extern BUN HASH_DESTROY_UNIQUES_FRACTION
/* if the estimated number of unique values is less than 1 in this
* number, don't build a hash table to do a hashselect */
extern dbl NO_HASH_SELECT_FRACTION; /* same here */
+/* if the hash chain is longer than this number, we delete the hash
+ * rather than maintaining it in HASHdelete */
+extern BUN HASH_DESTROY_CHAIN_LENGTH;
#if !defined(NDEBUG) && !defined(__COVERITY__)
/* see comment in gdk.h */
diff --git a/gdk/gdk_utils.c b/gdk/gdk_utils.c
--- a/gdk/gdk_utils.c
+++ b/gdk/gdk_utils.c
@@ -66,6 +66,9 @@ BUN HASH_DESTROY_UNIQUES_FRACTION = 1000
/* if the estimated number of unique values is less than 1 in this
* number, don't build a hash table to do a hashselect */
dbl NO_HASH_SELECT_FRACTION = 1000; /* same here */
+/* if the hash chain is longer than this number, we delete the hash
+ * rather than maintaining it in HASHdelete */
+BUN HASH_DESTROY_CHAIN_LENGTH = 1000;
/*
* @+ Monet configuration file
@@ -1169,6 +1172,11 @@ GDKinit(opt *set, int setlen, bool embed
NO_HASH_SELECT_FRACTION = (dbl) strtoll(p, NULL, 10);
if (NO_HASH_SELECT_FRACTION == 0)
NO_HASH_SELECT_FRACTION = (dbl)
GDK_UNIQUE_ESTIMATE_KEEP_FRACTION;
+ HASH_DESTROY_CHAIN_LENGTH = 0;
+ if ((p = GDKgetenv("hash_destroy_chain_length")) != NULL)
+ HASH_DESTROY_CHAIN_LENGTH = (BUN) strtoll(p, NULL, 10);
+ if (HASH_DESTROY_CHAIN_LENGTH == 0)
+ HASH_DESTROY_CHAIN_LENGTH = 1000;
return GDK_SUCCEED;
}
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