ZSET B+ Tree PR 1: extract skiplist into dedicated module

cmake/Modules/SourceFiles.cmake

@@ -33,6 +33,7 @@ set(VALKEY_SERVER_SRCS
     ${CMAKE_SOURCE_DIR}/src/t_list.c
     ${CMAKE_SOURCE_DIR}/src/t_set.c
     ${CMAKE_SOURCE_DIR}/src/t_zset.c
+    ${CMAKE_SOURCE_DIR}/src/skiplist.c
     ${CMAKE_SOURCE_DIR}/src/t_hash.c
     ${CMAKE_SOURCE_DIR}/src/config.c
     ${CMAKE_SOURCE_DIR}/src/aof.c

src/Makefile

@@ -567,6 +567,7 @@ ENGINE_SERVER_OBJ = \
     t_stream.o \
     t_string.o \
     t_zset.o \
+    skiplist.o \
     threads_mngr.o \
     timeout.o \
     tls.o \

src/aof.c

@@ -28,6 +28,7 @@
  */
 
 #include "server.h"
+#include "skiplist.h"
 #include "bio.h"
 #include "rio.h"
 #include "functions.h"

src/db.c

@@ -28,6 +28,7 @@
  */
 
 #include "server.h"
+#include "skiplist.h"
 #include "cluster.h"
 #include "cluster_migrateslots.h"
 #include "latency.h"

src/debug.c

@@ -28,6 +28,7 @@
  */
 
 #include "server.h"
+#include "skiplist.h"
 #include "util.h"
 #include "sha1.h" /* SHA1 is used for DEBUG DIGEST */
 #include "crc64.h"

src/defrag.c

@@ -39,6 +39,7 @@
  */
 
 #include "server.h"
+#include "skiplist.h"
 #include "hashtable.h"
 #include "eval.h"
 #include "script.h"

src/geo.c

@@ -29,6 +29,7 @@
  */
 
 #include "geo.h"
+#include "skiplist.h"
 #include "geohash_helper.h"
 #include "debugmacro.h"
 #include "pqsort.h"

src/lazyfree.c

@@ -1,4 +1,5 @@
 #include "server.h"
+#include "skiplist.h"
 #include "bio.h"
 #include "functions.h"
 #include "cluster.h"

src/module.c

@@ -56,6 +56,7 @@
  * function names. For details, see the script src/modules/gendoc.rb.
  * -------------------------------------------------------------------------- */
 #include "server.h"
+#include "skiplist.h"
 #include "cluster.h"
 #include "commandlog.h"
 #include "rdb.h"

src/object.c

@@ -30,6 +30,7 @@
 
 #include "hashtable.h"
 #include "server.h"
+#include "skiplist.h"
 #include "serverassert.h"
 #include "functions.h"
 #include "intset.h" /* Compact integer set structure */

src/rdb.c

@@ -34,6 +34,7 @@
 
 #include "hashtable.h"
 #include "server.h"
+#include "skiplist.h"
 #include "lzf.h" /* LZF compression library */
 #include "zipmap.h"
 #include "endianconv.h"

src/server.c

@@ -32,6 +32,7 @@
  * SPDX-License-Identifier: BSD-3-Clause
  */
 #include "server.h"
+#include "skiplist.h"
 #include "connection.h"
 #include "monotonic.h"
 #include "cluster.h"

src/server.h

@@ -497,8 +497,6 @@ typedef enum {
 #define SUPERVISED_SYSTEMD 2
 #define SUPERVISED_UPSTART 3
 
-#define ZSKIPLIST_MAXLEVEL 32 /* Should be enough for 2^64 elements */
-#define ZSKIPLIST_MAX_SEARCH 10
 
 /* Append only defines */
 #define REPL_MAX_WRITTEN_BEFORE_FSYNC (1024 * 1024 * 8) /* 8 MB */
@@ -1490,41 +1488,12 @@ struct sharedObjectsStruct {
     sds minstring, maxstring;
 };
 
-/* ZSETs use a specialized version of Skiplists */
-typedef struct zskiplistNode {
-    union {
-        double score;         /* Sorting score for node ordering. */
-        unsigned long length; /* Number of elements in the skiplist. */
-    };
-    union {
-        struct zskiplistNode *backward; /* Pointer to previous node for reverse traversal. */
-        struct zskiplistNode *tail;     /* Tail element of the skiplist. */
-    };
-    struct zskiplistLevel {
-        struct zskiplistNode *forward;
-        /* At each level we keep the span, which is the number of elements which are on the "subtree"
-         * from this node at this level to the next node at the same level.
-         * One exception is the value at level 0. In level 0 the span can only be 1 or 0 (in case the last elements in the list)
-         * So we use it in order to hold the height of the node, which is the number of levels. */
-        unsigned long span;
-    } level[1]; /* Flexible array member - actual levels determined at node creation. */
-    /* For non-header nodes, after the level[], sds header length (1 byte) and an embedded sds element are stored. */
-} zskiplistNode;
-
-/* The header node does not store actual data (no score, no backward pointer,
- * and its node height is fixed at ZSKIPLIST_MAXLEVEL).
- * To save memory, we reuse the memory space of these fields in the header node to store:
- *   - skiplist length (number of elements)
- *   - tail pointer to the last element
- *   - maximum current level of the skiplist
- * For detailed memory layout, refer to the zskiplistNode struct definition. */
-typedef struct zskiplist {
-    zskiplistNode header;
-} zskiplist;
+/* Skiplist types - full definitions in skiplist.h */
+struct zskiplist;
 
 typedef struct zset {
     hashtable *ht;
-    zskiplist *zsl;
+    struct zskiplist *zsl;
 } zset;
 
 typedef struct clientBufferLimitsConfig {
@@ -3401,17 +3370,6 @@ typedef struct {
 #define ERROR_COMMAND_REJECTED (1 << 0) /* Indicate to update the command rejected stats */
 #define ERROR_COMMAND_FAILED (1 << 1)   /* Indicate to update the command failed stats */
 
-zskiplist *zslCreate(void);
-int zslGetHeight(const zskiplist *zsl);
-zskiplistNode *zslGetTail(const zskiplist *zsl);
-void zslSetTail(zskiplist *zsl, zskiplistNode *tail);
-unsigned long zslGetLength(const zskiplist *zsl);
-zskiplistNode *zslGetHeader(zskiplist *zsl);
-size_t zslGetAllocSize(void);
-void zslFree(zskiplist *zsl);
-zskiplistNode *zslInsert(zskiplist *zsl, double score, const_sds ele);
-zskiplistNode *zslNthInRange(zskiplist *zsl, zrangespec *range, long n, long *rank);
-sds zslGetNodeElement(const zskiplistNode *x);
 double zzlGetScore(unsigned char *sptr);
 void zzlNext(unsigned char *zl, unsigned char **eptr, unsigned char **sptr);
 void zzlPrev(unsigned char *zl, unsigned char **eptr, unsigned char **sptr);
@@ -3434,17 +3392,12 @@ void genericZpopCommand(client *c,
                         int reply_nil_when_empty,
                         int *deleted);
 sds lpGetObject(unsigned char *sptr);
-int zslValueGteMin(double value, zrangespec *spec);
-int zslValueLteMax(double value, zrangespec *spec);
 void zsetFreeLexRange(zlexrangespec *spec);
 int zsetParseLexRange(robj *min, robj *max, zlexrangespec *spec);
 unsigned char *zzlFirstInLexRange(unsigned char *zl, zlexrangespec *range);
 unsigned char *zzlLastInLexRange(unsigned char *zl, zlexrangespec *range);
-zskiplistNode *zslNthInLexRange(zskiplist *zsl, zlexrangespec *range, long n);
 int zzlLexValueGteMin(unsigned char *p, zlexrangespec *spec);
 int zzlLexValueLteMax(unsigned char *p, zlexrangespec *spec);
-int zslLexValueGteMin(sds value, zlexrangespec *spec);
-int zslLexValueLteMax(sds value, zlexrangespec *spec);
 
 /* Core functions */
 int getMaxmemoryState(size_t *total, size_t *logical, size_t *tofree, float *level);