From 8361d6c406fec73106c627159f28e092cedef1ee Mon Sep 17 00:00:00 2001
From: antirez <antirez@gmail.com>
Date: Thu, 14 Jun 2012 15:59:25 +0200
Subject: [PATCH] ziplistFind(): don't assume that entries are comparable by
encoding.
Because Redis 2.6 introduced new integer encodings it is no longer true
that if two entries have a different encoding they are not equal.
An old ziplist can be loaded from an RDB file generated with Redis 2.4,
in this case for instance a small unsigned integers is encoded with a
16 bit encoding, while in Redis 2.6 a more specific 8 bit encoding
format is used.
Because of this bug hashes ended with duplicated values or fields lookup
failed, causing many bad behaviors.
This in turn caused a crash while converting the ziplist encoded hash into
a real hash table because an assertion was raised on duplicated elements.
This commit fixes issue #547.
Many thanks to Pinterest's Marty Weiner and colleagues for discovering
the problem and helping us in the debugging process.
---
src/ziplist.c | 15 ++++++++++-----
1 file changed, 10 insertions(+), 5 deletions(-)
diff --git a/src/ziplist.c b/src/ziplist.c
index 31e61633..50167651 100644
--- a/src/ziplist.c
+++ b/src/ziplist.c
@@ -805,19 +805,24 @@ unsigned char *ziplistFind(unsigned char *p, unsigned char *vstr, unsigned int v
return p;
}
} else {
- /* Find out if the specified entry can be encoded */
+ /* Find out if the searched field can be encoded. Note that
+ * we do it only the first time, once done vencoding is set
+ * to non-zero and vll is set to the integer value. */
if (vencoding == 0) {
- /* UINT_MAX when the entry CANNOT be encoded */
if (!zipTryEncoding(vstr, vlen, &vll, &vencoding)) {
+ /* If the entry can't be encoded we set it to
+ * UCHAR_MAX so that we don't retry again the next
+ * time. */
vencoding = UCHAR_MAX;
}
-
/* Must be non-zero by now */
assert(vencoding);
}
- /* Compare current entry with specified entry */
- if (encoding == vencoding) {
+ /* Compare current entry with specified entry, do it only
+ * if vencoding != UCHAR_MAX because if there is no encoding
+ * possible for the field it can't be a valid integer. */
+ if (vencoding != UCHAR_MAX) {
long long ll = zipLoadInteger(q, encoding);
if (ll == vll) {
return p;
--
2.49.0