Remove the bucket-cb from dictScan and move dictEntry defrag to dictScanDefrag

This change deletes the dictGetNext and dictGetNextRef functions, so the
dict API doesn't expose the next field at all.

The bucket function in dictScan is deleted. A separate dictScanDefrag function
is added which takes a defrag alloc function to defrag-reallocate the dict entries.

"Dirty" code accessing the dict internals in active defrag is removed.

An 'afterReplaceEntry' is added to dictType, which allows the dict user
to keep the dictEntry metadata up to date after reallocation/defrag/move.

Additionally, for updating the cluster slot-to-key mapping, after a dictEntry
has been reallocated, we need to know which db a dict belongs to, so we store
a pointer to the db in a new metadata section in the dict struct, which is
a new mechanism similar to dictEntry metadata. This adds some complexity but
provides better isolation.

1 files changed, 15 insertions, 2 deletions

diff --git a/src/server.c b/src/server.c
index ae83ec25c..910f299f3 100644
--- a/src/server.c
+++ b/src/server.c
@@ -399,13 +399,24 @@ int dictExpandAllowed(size_t moreMem, double usedRatio) {
 /* Returns the size of the DB dict entry metadata in bytes. In cluster mode, the
  * metadata is used for constructing a doubly linked list of the dict entries
  * belonging to the same cluster slot. See the Slot to Key API in cluster.c. */
-size_t dictEntryMetadataSize(dict *d) {
+size_t dbDictEntryMetadataSize(dict *d) {
     UNUSED(d);
     /* NOTICE: this also affects overhead_ht_slot_to_keys in getMemoryOverheadData.
      * If we ever add non-cluster related data here, that code must be modified too. */
     return server.cluster_enabled ? sizeof(clusterDictEntryMetadata) : 0;
 }
 
+/* Returns the size of the DB dict metadata in bytes. In cluster mode, we store
+ * a pointer to the db in the main db dict, used for updating the slot-to-key
+ * mapping when a dictEntry is reallocated. */
+size_t dbDictMetadataSize(void) {
+    return server.cluster_enabled ? sizeof(clusterDictMetadata) : 0;
+}
+
+void dbDictAfterReplaceEntry(dict *d, dictEntry *de) {
+    if (server.cluster_enabled) slotToKeyReplaceEntry(d, de);
+}
+
 /* Generic hash table type where keys are Redis Objects, Values
  * dummy pointers. */
 dictType objectKeyPointerValueDictType = {
@@ -460,7 +471,9 @@ dictType dbDictType = {
     dictSdsDestructor,          /* key destructor */
     dictObjectDestructor,       /* val destructor */
     dictExpandAllowed,          /* allow to expand */
-    dictEntryMetadataSize       /* size of entry metadata in bytes */
+    dbDictEntryMetadataSize,    /* size of entry metadata in bytes */
+    dbDictMetadataSize,         /* size of dict metadata in bytes */
+    dbDictAfterReplaceEntry     /* notify entry moved/reallocated */
 };
 
 /* Db->expires */