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Refactor the per-slot dict-array db.c into a new kvstore data structure (#12822)

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# Description
Gather most of the scattered `redisDb`-related code from the per-slot
dict PR (#11695) and turn it to a new data structure, `kvstore`. i.e.
it's a class that represents an array of dictionaries.

# Motivation
The main motivation is code cleanliness, the idea of using an array of
dictionaries is very well-suited to becoming a self-contained data
structure.
This allowed cleaning some ugly code, among others: loops that run twice
on the main dict and expires dict, and duplicate code for allocating and
releasing this data structure.

# Notes
1. This PR reverts the part of https://github.com/redis/redis/pull/12848
where the `rehashing` list is global (handling rehashing `dict`s is
under the responsibility of `kvstore`, and should not be managed by the
server)
2. This PR also replaces the type of `server.pubsubshard_channels` from
`dict**` to `kvstore` (original PR:
https://github.com/redis/redis/pull/12804). After that was done,
server.pubsub_channels was also chosen to be a `kvstore` (with only one
`dict`, which seems odd) just to make the code cleaner by making it the
same type as `server.pubsubshard_channels`, see
`pubsubtype.serverPubSubChannels`
3. the keys and expires kvstores are currenlty configured to allocate
the individual dicts only when the first key is added (unlike before, in
which they allocated them in advance), but they won't release them when
the last key is deleted.

Worth mentioning that due to the recent change the reply of DEBUG
HTSTATS changed, in case no keys were ever added to the db.

before:
```
127.0.0.1:6379> DEBUG htstats 9
[Dictionary HT]
Hash table 0 stats (main hash table):
No stats available for empty dictionaries
[Expires HT]
Hash table 0 stats (main hash table):
No stats available for empty dictionaries
```

after:
```
127.0.0.1:6379> DEBUG htstats 9
[Dictionary HT]
[Expires HT]
```
This commit is contained in:
guybe7
2024-02-05 17:21:35 +02:00
committed by GitHub
parent f20774eced
commit 8cd62f82ca
23 changed files with 1126 additions and 927 deletions
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src/multi.c
+4 -4
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@@ -394,7 +394,7 @@ void touchWatchedKey(redisDb *db, robj *key) {
/* The key was already expired when WATCH was called. */
if (db == wk->db &&
equalStringObjects(key, wk->key) &&
dictFind(db->dict[calculateKeySlot(key->ptr)], key->ptr) == NULL)
dbFind(db, key->ptr) == NULL)
{
/* Already expired key is deleted, so logically no change. Clear
* the flag. Deleted keys are not flagged as expired. */
@@ -432,9 +432,9 @@ void touchAllWatchedKeysInDb(redisDb *emptied, redisDb *replaced_with) {
dictIterator *di = dictGetSafeIterator(emptied->watched_keys);
while((de = dictNext(di)) != NULL) {
robj *key = dictGetKey(de);
int exists_in_emptied = dictFind(emptied->dict[calculateKeySlot(key->ptr)], key->ptr) != NULL;
int exists_in_emptied = dbFind(emptied, key->ptr) != NULL;
if (exists_in_emptied ||
(replaced_with && dictFind(replaced_with->dict[calculateKeySlot(key->ptr)], key->ptr)))
(replaced_with && dbFind(replaced_with, key->ptr) != NULL))
{
list *clients = dictGetVal(de);
if (!clients) continue;
@@ -442,7 +442,7 @@ void touchAllWatchedKeysInDb(redisDb *emptied, redisDb *replaced_with) {
while((ln = listNext(&li))) {
watchedKey *wk = redis_member2struct(watchedKey, node, ln);
if (wk->expired) {
if (!replaced_with || !dictFind(replaced_with->dict[calculateKeySlot(key->ptr)], key->ptr)) {
if (!replaced_with || !dbFind(replaced_with, key->ptr)) {
/* Expired key now deleted. No logical change. Clear the
* flag. Deleted keys are not flagged as expired. */
wk->expired = 0;