FT-273 Use a comparator object for fractal tree key comparisons when

possible, untangling the dependency between parameters 'ft->compare_fun' and
'ft->cmp_descriptor' in a sensible way. It is now much less necessary to
create a fake db (good) and some long parameter lists are now shorter
(it's a start)

ft/comparator.h

@@ -95,36 +95,51 @@ PATENT RIGHTS GRANT:
 
 #include <ft/ybt.h>
 #include <ft/fttypes.h>
+#include <portability/memory.h>
 
 namespace toku {
 
-// a comparator object encapsulates the data necessary for 
-// comparing two keys in a fractal tree. it further understands
-// that points may be positive or negative infinity.
-
-class comparator {
-public:
-    void set_descriptor(DESCRIPTOR desc) {
-        m_fake_db.cmp_descriptor = desc;
-    }
-
-    void create(ft_compare_func cmp, DESCRIPTOR desc) {
-        m_cmp = cmp;
-        memset(&m_fake_db, 0, sizeof(m_fake_db));
-        m_fake_db.cmp_descriptor = desc;
-    }
-
-    int compare(const DBT *a, const DBT *b) {
-        if (toku_dbt_is_infinite(a) || toku_dbt_is_infinite(b)) {
-            return toku_dbt_infinite_compare(a, b);
-        } else {
-            return m_cmp(&m_fake_db, a, b);
+    // a comparator object encapsulates the data necessary for 
+    // comparing two keys in a fractal tree. it further understands
+    // that points may be positive or negative infinity.
+
+    class comparator {
+    public:
+        void create(ft_compare_func cmp, DESCRIPTOR desc) {
+            _cmp = cmp;
+            XCALLOC(_fake_db);
+            _fake_db->cmp_descriptor = desc;
+        }
+
+        void destroy() {
+            toku_free(_fake_db);
+        }
+
+        const DESCRIPTOR_S *get_descriptor() const {
+            return _fake_db->cmp_descriptor;
+        }
+
+        ft_compare_func get_compare_func() const {
+            return _cmp;
+        }
+
+        void set_descriptor(DESCRIPTOR desc) {
+            _fake_db->cmp_descriptor = desc;
+        }
+
+        int operator()(const DBT *a, const DBT *b) const {
+            // TODO: add an unlikely() compiler note for this branch
+            if (toku_dbt_is_infinite(a) || toku_dbt_is_infinite(b)) {
+                return toku_dbt_infinite_compare(a, b);
+            } else {
+                // yikes, const sadness here
+                return _cmp(const_cast<DB *>(_fake_db), a, b);
+            }
         }
-    }
 
-private:
-    struct __toku_db m_fake_db;
-    ft_compare_func m_cmp;
-};
+    private:
+        DB *_fake_db;
+        ft_compare_func _cmp;
+    };
 
 } /* namespace toku */

ft/cursor.cc

@@ -213,8 +213,7 @@ static int ft_cursor_search(FT_CURSOR cursor, ft_search *search,
 }
 
 static inline int compare_k_x(FT_HANDLE ft_handle, const DBT *k, const DBT *x) {
-    FAKE_DB(db, &ft_handle->ft->cmp_descriptor);
-    return ft_handle->ft->compare_fun(&db, k, x);
+    return ft_handle->ft->cmp(k, x);
 }
 
 int toku_ft_cursor_compare_one(const ft_search &UU(search), const DBT *UU(x)) {
@@ -290,11 +289,10 @@ int toku_ft_cursor_last(FT_CURSOR cursor, FT_GET_CALLBACK_FUNCTION getf, void *g
 int toku_ft_cursor_check_restricted_range(FT_CURSOR c, bytevec key, ITEMLEN keylen) {
     if (c->out_of_range_error) {
         FT ft = c->ft_handle->ft;
-        FAKE_DB(db, &ft->cmp_descriptor);
         DBT found_key;
         toku_fill_dbt(&found_key, key, keylen);
-        if ((!c->left_is_neg_infty && c->direction <= 0 && ft->compare_fun(&db, &found_key, &c->range_lock_left_key) < 0) ||
-            (!c->right_is_pos_infty && c->direction >= 0 && ft->compare_fun(&db, &found_key, &c->range_lock_right_key) > 0)) {
+        if ((!c->left_is_neg_infty && c->direction <= 0 && ft->cmp(&found_key, &c->range_lock_left_key) < 0) ||
+            (!c->right_is_pos_infty && c->direction >= 0 && ft->cmp(&found_key, &c->range_lock_right_key) > 0)) {
             invariant(c->out_of_range_error);
             return c->out_of_range_error;
         }

ft/ft-flusher.cc

@@ -406,13 +406,8 @@ ctm_pick_child(FT ft,
     int childnum;
     if (parent->height == 1 && ctme->is_last_child) {
         childnum = parent->n_children - 1;
-    }
-    else {
-        childnum = toku_ftnode_which_child(
-            parent,
-            &ctme->target_key,
-            &ft->cmp_descriptor,
-            ft->compare_fun);
+    } else {
+        childnum = toku_ftnode_which_child(parent, &ctme->target_key, ft->cmp);
     }
     return childnum;
 }
@@ -1703,9 +1698,8 @@ void toku_bnc_flush_to_child(FT ft, NONLEAF_CHILDINFO bnc, FTNODE child, TXNID p
                 flow_deltas[1] = memsize_in_buffer;
             }
             toku_ftnode_put_msg(
-                ft->compare_fun,
+                ft->cmp,
                 ft->update_fun,
-                &ft->cmp_descriptor,
                 child,
                 -1,
                 msg,

ft/ft-hot-flusher.cc

@@ -184,10 +184,7 @@ hot_just_pick_child(FT ft,
         childnum = 0;
     } else {
         // Find the pivot boundary.
-        childnum = toku_ftnode_hot_next_child(parent,
-                                               &flusher->highest_pivot_key,
-                                               &ft->cmp_descriptor,
-                                               ft->compare_fun);
+        childnum = toku_ftnode_hot_next_child(parent, &flusher->highest_pivot_key, ft->cmp);
     }
 
     return childnum;
@@ -386,8 +383,7 @@ toku_ft_hot_optimize(FT_HANDLE ft_handle, DBT* left, DBT* right,
         else if (right) {
             // if we have flushed past the bounds set for us,
             // set rightmost_leaf_seen so we exit
-            FAKE_DB(db, &ft_handle->ft->cmp_descriptor);
-            int cmp = ft_handle->ft->compare_fun(&db, &flusher.max_current_key, right);
+            int cmp = ft_handle->ft->cmp(&flusher.max_current_key, right);
             if (cmp > 0) {
                 flusher.rightmost_leaf_seen = 1;
             }

ft/ft-internal.h

@@ -111,9 +111,9 @@ PATENT RIGHTS GRANT:
 #include "leafentry.h"
 #include "block_table.h"
 #include "compress.h"
-#include <util/mempool.h>
 #include <util/omt.h>
 #include "ft/bndata.h"
+#include "ft/comparator.h"
 #include "ft/rollback.h"
 #include "ft/msg_buffer.h"
 
@@ -213,15 +213,18 @@ struct ft {
     CACHEFILE cf;
     // unique id for dictionary
     DICTIONARY_ID dict_id;
-    ft_compare_func compare_fun;
-    ft_update_func update_fun;
 
     // protected by locktree
     DESCRIPTOR_S descriptor;
-    // protected by locktree and user. User 
-    // makes sure this is only changed
-    // when no activity on tree
+
+    // protected by locktree and user.
+    // User makes sure this is only changed when no activity on tree
     DESCRIPTOR_S cmp_descriptor;
+    // contains a pointer to cmp_descriptor (above) - their lifetimes are bound
+    toku::comparator cmp;
+
+    // the update function always utilizes the cmp_descriptor, not the regular one
+    ft_update_func update_fun;
 
     // These are not read-only:
 
@@ -272,7 +275,7 @@ typedef struct ft *FT;
 // descriptor. We don't bother setting any other fields because
 // the comparison function doesn't need it, and we would like to
 // reduce the CPU work done per comparison.
-#define FAKE_DB(db, desc) struct __toku_db db; do { db.cmp_descriptor = desc; } while (0)
+#define FAKE_DB(db, desc) struct __toku_db db; do { db.cmp_descriptor = const_cast<DESCRIPTOR>(desc); } while (0)
 
 struct ft_options {
     unsigned int nodesize;
@@ -390,14 +393,14 @@ void toku_serialize_ft_to_wbuf (
     DISKOFF translation_size_on_disk
     );
 int toku_deserialize_ft_from (int fd, LSN max_acceptable_lsn, FT *ft);
-void toku_serialize_descriptor_contents_to_fd(int fd, const DESCRIPTOR desc, DISKOFF offset);
-void toku_serialize_descriptor_contents_to_wbuf(struct wbuf *wb, const DESCRIPTOR desc);
+void toku_serialize_descriptor_contents_to_fd(int fd, DESCRIPTOR desc, DISKOFF offset);
+void toku_serialize_descriptor_contents_to_wbuf(struct wbuf *wb, DESCRIPTOR desc);
 
 // append a child node to a parent node
 void toku_ft_nonleaf_append_child(FTNODE node, FTNODE child, const DBT *pivotkey);
 
 // append a message to a nonleaf node child buffer
-void toku_ft_append_to_child_buffer(ft_compare_func compare_fun, DESCRIPTOR desc, FTNODE node, int childnum, enum ft_msg_type type, MSN msn, XIDS xids, bool is_fresh, const DBT *key, const DBT *val);
+void toku_ft_append_to_child_buffer(const toku::comparator &cmp, FTNODE node, int childnum, enum ft_msg_type type, MSN msn, XIDS xids, bool is_fresh, const DBT *key, const DBT *val);
 
 STAT64INFO_S toku_get_and_clear_basement_stats(FTNODE leafnode);
 

ft/ft-ops.h

@@ -110,7 +110,7 @@ int toku_open_ft_handle (const char *fname, int is_create, FT_HANDLE *, int node
 //   ANY operations. to update the cmp descriptor after any operations have already happened, all handles 
 //   and transactions must close and reopen before the change, then you can update the cmp descriptor
 void toku_ft_change_descriptor(FT_HANDLE t, const DBT* old_descriptor, const DBT* new_descriptor, bool do_log, TOKUTXN txn, bool update_cmp_descriptor);
-uint32_t toku_serialize_descriptor_size(const DESCRIPTOR desc);
+uint32_t toku_serialize_descriptor_size(DESCRIPTOR desc);
 
 void toku_ft_handle_create(FT_HANDLE *ft);
 void toku_ft_set_flags(FT_HANDLE, unsigned int flags);

ft/ft-serialize.cc

@@ -95,7 +95,7 @@ PATENT RIGHTS GRANT:
 
 // not version-sensitive because we only serialize a descriptor using the current layout_version
 uint32_t
-toku_serialize_descriptor_size(const DESCRIPTOR desc) {
+toku_serialize_descriptor_size(DESCRIPTOR desc) {
     //Checksum NOT included in this.  Checksum only exists in header's version.
     uint32_t size = 4; // four bytes for size of descriptor
     size += desc->dbt.size;
@@ -103,7 +103,7 @@ toku_serialize_descriptor_size(const DESCRIPTOR desc) {
 }
 
 static uint32_t
-deserialize_descriptor_size(const DESCRIPTOR desc, int layout_version) {
+deserialize_descriptor_size(DESCRIPTOR desc, int layout_version) {
     //Checksum NOT included in this.  Checksum only exists in header's version.
     uint32_t size = 4; // four bytes for size of descriptor
     if (layout_version == FT_LAYOUT_VERSION_13)
@@ -112,8 +112,7 @@ deserialize_descriptor_size(const DESCRIPTOR desc, int layout_version) {
     return size;
 }
 
-void
-toku_serialize_descriptor_contents_to_wbuf(struct wbuf *wb, const DESCRIPTOR desc) {
+void toku_serialize_descriptor_contents_to_wbuf(struct wbuf *wb, DESCRIPTOR desc) {
     wbuf_bytes(wb, desc->dbt.data, desc->dbt.size);
 }
 
@@ -121,7 +120,7 @@ toku_serialize_descriptor_contents_to_wbuf(struct wbuf *wb, const DESCRIPTOR des
 //descriptor.
 //Descriptors are NOT written during the header checkpoint process.
 void
-toku_serialize_descriptor_contents_to_fd(int fd, const DESCRIPTOR desc, DISKOFF offset) {
+toku_serialize_descriptor_contents_to_fd(int fd, DESCRIPTOR desc, DISKOFF offset) {
     // make the checksum
     int64_t size = toku_serialize_descriptor_size(desc)+4; //4 for checksum
     int64_t size_aligned = roundup_to_multiple(512, size);
@@ -437,7 +436,8 @@ int deserialize_ft_versioned(int fd, struct rbuf *rb, FT *ftp, uint32_t version)
     if (r != 0) {
         goto exit;
     }
-    // copy descriptor to cmp_descriptor for #4541
+    // initialize for svn #4541
+    // TODO: use real dbt function
     ft->cmp_descriptor.dbt.size = ft->descriptor.dbt.size;
     ft->cmp_descriptor.dbt.data = toku_xmemdup(ft->descriptor.dbt.data, ft->descriptor.dbt.size);
     // Version 13 descriptors had an extra 4 bytes that we don't read

ft/ft-test-helpers.cc

@@ -225,9 +225,8 @@ int toku_testsetup_insert_to_leaf (FT_HANDLE ft_handle, BLOCKNUM blocknum, const
     static size_t zero_flow_deltas[] = { 0, 0 };
     txn_gc_info gc_info(nullptr, TXNID_NONE, TXNID_NONE, true);
     toku_ftnode_put_msg(
-        ft_handle->ft->compare_fun,
+        ft_handle->ft->cmp,
         ft_handle->ft->update_fun,
-        &ft_handle->ft->cmp_descriptor,
         node,
         -1,
         &msg,
@@ -293,13 +292,14 @@ int toku_testsetup_insert_to_nonleaf (FT_HANDLE ft_handle, BLOCKNUM blocknum, en
     assert(node->height>0);
 
     DBT k;
-    int childnum = toku_ftnode_which_child(node,
-                                            toku_fill_dbt(&k, key, keylen),
-                                            &ft_handle->ft->cmp_descriptor, ft_handle->ft->compare_fun);
+    int childnum = toku_ftnode_which_child(node, toku_fill_dbt(&k, key, keylen), ft_handle->ft->cmp);
 
     XIDS xids_0 = xids_get_root_xids();
     MSN msn = next_dummymsn();
-    toku_bnc_insert_msg(BNC(node, childnum), key, keylen, val, vallen, msgtype, msn, xids_0, true, NULL, testhelper_string_key_cmp);
+    toku::comparator cmp;
+    cmp.create(testhelper_string_key_cmp, nullptr);
+    toku_bnc_insert_msg(BNC(node, childnum), key, keylen, val, vallen, msgtype, msn, xids_0, true, cmp);
+    cmp.destroy();
     // Hack to get the test working. The problem is that this test
     // is directly queueing something in a FIFO instead of 
     // using ft APIs.

ft/ft-verify.cc

@@ -104,17 +104,13 @@ PATENT RIGHTS GRANT:
 
 static int 
 compare_pairs (FT_HANDLE ft_handle, const DBT *a, const DBT *b) {
-    FAKE_DB(db, &ft_handle->ft->cmp_descriptor);
-    int cmp = ft_handle->ft->compare_fun(&db, a, b);
-    return cmp;
+    return ft_handle->ft->cmp(a, b);
 }
 
 static int 
 compare_pair_to_key (FT_HANDLE ft_handle, const DBT *a, bytevec key, ITEMLEN keylen) {
     DBT y;
-    FAKE_DB(db, &ft_handle->ft->cmp_descriptor);
-    int cmp = ft_handle->ft->compare_fun(&db, a, toku_fill_dbt(&y, key, keylen));
-    return cmp;
+    return ft_handle->ft->cmp(a, toku_fill_dbt(&y, key, keylen));
 }
 
 static int
@@ -256,11 +252,7 @@ verify_sorted_by_key_msn(FT_HANDLE ft_handle, message_buffer *msg_buffer, const
         int r = mt.fetch(i, &offset);
         assert_zero(r);
         if (i > 0) {
-            struct toku_msg_buffer_key_msn_cmp_extra extra;
-            ZERO_STRUCT(extra);
-            extra.desc = &ft_handle->ft->cmp_descriptor;
-            extra.cmp = ft_handle->ft->compare_fun;
-            extra.msg_buffer = msg_buffer;
+            struct toku_msg_buffer_key_msn_cmp_extra extra(ft_handle->ft->cmp, msg_buffer);
             if (toku_msg_buffer_key_msn_cmp(extra, last_offset, offset) >= 0) {
                 result = TOKUDB_NEEDS_REPAIR;
                 break;
@@ -274,13 +266,7 @@ verify_sorted_by_key_msn(FT_HANDLE ft_handle, message_buffer *msg_buffer, const
 template<typename count_omt_t>
 static int
 count_eq_key_msn(FT_HANDLE ft_handle, message_buffer *msg_buffer, const count_omt_t &mt, const DBT *key, MSN msn) {
-    struct toku_msg_buffer_key_msn_heaviside_extra extra;
-    ZERO_STRUCT(extra);
-    extra.desc = &ft_handle->ft->cmp_descriptor;
-    extra.cmp = ft_handle->ft->compare_fun;
-    extra.msg_buffer = msg_buffer;
-    extra.key = key;
-    extra.msn = msn;
+    struct toku_msg_buffer_key_msn_heaviside_extra extra(ft_handle->ft->cmp, msg_buffer, key, msn);
     int r = mt.template find_zero<struct toku_msg_buffer_key_msn_heaviside_extra, toku_msg_buffer_key_msn_heaviside>(extra, nullptr, nullptr);
     int count;
     if (r == 0) {

ft/ft.cc

@@ -119,7 +119,10 @@ ft_destroy(FT ft) {
     //cannot destroy since it is still in use by CURRENT
     assert(ft->h->type == FT_CURRENT);
     toku_blocktable_destroy(&ft->blocktable);
+    ft->cmp.destroy();
+    // TODO: use real dbt function
     if (ft->descriptor.dbt.data) toku_free(ft->descriptor.dbt.data);
+    // TODO: use real dbt function
     if (ft->cmp_descriptor.dbt.data) toku_free(ft->cmp_descriptor.dbt.data);
     toku_ft_destroy_reflock(ft);
     toku_free(ft->h);
@@ -384,7 +387,7 @@ static void ft_init(FT ft, FT_OPTIONS options, CACHEFILE cf) {
 
     toku_list_init(&ft->live_ft_handles);
 
-    ft->compare_fun = options->compare_fun;
+    ft->cmp.create(options->compare_fun, &ft->descriptor);
     ft->update_fun = options->update_fun;
 
     if (ft->cf != NULL) {
@@ -449,9 +452,6 @@ void toku_ft_create(FT *ftp, FT_OPTIONS options, CACHEFILE cf, TOKUTXN txn) {
     invariant(ftp);
 
     FT XCALLOC(ft);
-    memset(&ft->descriptor, 0, sizeof(ft->descriptor));
-    memset(&ft->cmp_descriptor, 0, sizeof(ft->cmp_descriptor));
-
     ft->h = ft_header_create(options, make_blocknum(0), (txn ? txn->txnid.parent_id64: TXNID_NONE));
 
     toku_ft_init_reflock(ft);
@@ -471,31 +471,27 @@ int toku_read_ft_and_store_in_cachefile (FT_HANDLE ft_handle, CACHEFILE cf, LSN
 // If the cachefile has not been initialized, then don't modify anything.
 // max_acceptable_lsn is the latest acceptable checkpointed version of the file.
 {
-    {
-        FT ft;
-        if ((ft = (FT) toku_cachefile_get_userdata(cf))!=0) {
-            *header = ft;
-            assert(ft_handle->options.update_fun == ft->update_fun);
-            assert(ft_handle->options.compare_fun == ft->compare_fun);
-            return 0;
-        }
-    }
     FT ft = nullptr;
-    int r;
-    {
-        int fd = toku_cachefile_get_fd(cf);
-        r = toku_deserialize_ft_from(fd, max_acceptable_lsn, &ft);
-        if (r == TOKUDB_BAD_CHECKSUM) {
-            fprintf(stderr, "Checksum failure while reading header in file %s.\n", toku_cachefile_fname_in_env(cf));
-            assert(false);  // make absolutely sure we crash before doing anything else
-        }
+    if ((ft = (FT) toku_cachefile_get_userdata(cf)) != nullptr) {
+        *header = ft;
+        assert(ft_handle->options.update_fun == ft->update_fun);
+        return 0;
     }
-    if (r!=0) return r;
-    // GCC 4.8 seems to get confused by the gotos in the deserialize code and think h is maybe uninitialized.
+
+    int fd = toku_cachefile_get_fd(cf);
+    int r = toku_deserialize_ft_from(fd, max_acceptable_lsn, &ft);
+    if (r == TOKUDB_BAD_CHECKSUM) {
+        fprintf(stderr, "Checksum failure while reading header in file %s.\n", toku_cachefile_fname_in_env(cf));
+        assert(false);  // make absolutely sure we crash before doing anything else
+    } else if (r != 0) {
+        return r;
+    }
+
     invariant_notnull(ft);
-    ft->cf = cf;
-    ft->compare_fun = ft_handle->options.compare_fun;
+    // intuitively, the comparator points to the FT's cmp descriptor
+    ft->cmp.create(ft_handle->options.compare_fun, &ft->cmp_descriptor);
     ft->update_fun = ft_handle->options.update_fun;
+    ft->cf = cf;
     toku_cachefile_set_userdata(cf,
                                 reinterpret_cast<void *>(ft),
                                 ft_log_fassociate_during_checkpoint,
@@ -632,7 +628,7 @@ ft_handle_open_for_redirect(FT_HANDLE *new_ftp, const char *fname_in_env, TOKUTX
     FT_HANDLE ft_handle;
     assert(old_ft->dict_id.dictid != DICTIONARY_ID_NONE.dictid);
     toku_ft_handle_create(&ft_handle);
-    toku_ft_set_bt_compare(ft_handle, old_ft->compare_fun);
+    toku_ft_set_bt_compare(ft_handle, old_ft->cmp.get_compare_func());
     toku_ft_set_update(ft_handle, old_ft->update_fun);
     toku_ft_handle_set_nodesize(ft_handle, old_ft->h->nodesize);
     toku_ft_handle_set_basementnodesize(ft_handle, old_ft->h->basementnodesize);
@@ -890,7 +886,7 @@ int toku_ft_iterate_fractal_tree_block_map(FT ft, int (*iter)(uint64_t,int64_t,i
 }
 
 void 
-toku_ft_update_descriptor(FT ft, DESCRIPTOR d) 
+toku_ft_update_descriptor(FT ft, DESCRIPTOR desc) 
 // Effect: Changes the descriptor in a tree (log the change, make sure it makes it to disk eventually).
 // requires: the ft is fully user-opened with a valid cachefile.
 //           descriptor updates cannot happen in parallel for an FT 
@@ -898,7 +894,7 @@ toku_ft_update_descriptor(FT ft, DESCRIPTOR d)
 {
     assert(ft->cf);
     int fd = toku_cachefile_get_fd(ft->cf);
-    toku_ft_update_descriptor_with_fd(ft, d, fd);
+    toku_ft_update_descriptor_with_fd(ft, desc, fd);
 }
 
 // upadate the descriptor for an ft and serialize it using
@@ -907,27 +903,30 @@ toku_ft_update_descriptor(FT ft, DESCRIPTOR d)
 // update a descriptor before the ft is fully opened and has
 // a valid cachefile.
 void
-toku_ft_update_descriptor_with_fd(FT ft, DESCRIPTOR d, int fd) {
+toku_ft_update_descriptor_with_fd(FT ft, DESCRIPTOR desc, int fd) {
     // the checksum is four bytes, so that's where the magic number comes from
     // make space for the new descriptor and write it out to disk
     DISKOFF offset, size;
-    size = toku_serialize_descriptor_size(d) + 4;
+    size = toku_serialize_descriptor_size(desc) + 4;
     toku_realloc_descriptor_on_disk(ft->blocktable, size, &offset, ft, fd);
-    toku_serialize_descriptor_contents_to_fd(fd, d, offset);
+    toku_serialize_descriptor_contents_to_fd(fd, desc, offset);
 
     // cleanup the old descriptor and set the in-memory descriptor to the new one
+    // TODO: use real dbt function
     if (ft->descriptor.dbt.data) {
         toku_free(ft->descriptor.dbt.data);
     }
-    ft->descriptor.dbt.size = d->dbt.size;
-    ft->descriptor.dbt.data = toku_memdup(d->dbt.data, d->dbt.size);
+    // TODO: use real dbt function
+    ft->descriptor.dbt.size = desc->dbt.size;
+    ft->descriptor.dbt.data = toku_memdup(desc->dbt.data, desc->dbt.size);
 }
 
-void 
-toku_ft_update_cmp_descriptor(FT ft) {
+void toku_ft_update_cmp_descriptor(FT ft) {
+    // TODO: use real dbt function
     if (ft->cmp_descriptor.dbt.data != NULL) {
         toku_free(ft->cmp_descriptor.dbt.data);
     }
+    // TODO: use real dbt function
     ft->cmp_descriptor.dbt.size = ft->descriptor.dbt.size;
     ft->cmp_descriptor.dbt.data = toku_xmemdup(
         ft->descriptor.dbt.data, 
@@ -935,13 +934,11 @@ toku_ft_update_cmp_descriptor(FT ft) {
         );
 }
 
-DESCRIPTOR
-toku_ft_get_descriptor(FT_HANDLE ft_handle) {
+DESCRIPTOR toku_ft_get_descriptor(FT_HANDLE ft_handle) {
     return &ft_handle->ft->descriptor;
 }
 
-DESCRIPTOR
-toku_ft_get_cmp_descriptor(FT_HANDLE ft_handle) {
+DESCRIPTOR toku_ft_get_cmp_descriptor(FT_HANDLE ft_handle) {
     return &ft_handle->ft->cmp_descriptor;
 }
 

ft/ft.h

@@ -159,11 +159,11 @@ int toku_ft_iterate_fractal_tree_block_map(FT ft, int (*iter)(uint64_t,int64_t,i
 // any operation has already occurred on the ft.
 // see toku_ft_change_descriptor(), which is the transactional version
 // used by the ydb layer. it better describes the client contract.
-void toku_ft_update_descriptor(FT ft, DESCRIPTOR d);
+void toku_ft_update_descriptor(FT ft, DESCRIPTOR desc);
 // use this version if the FT is not fully user-opened with a valid cachefile.
 // this is a clean hack to get deserialization code to update a descriptor
 // while the FT and cf are in the process of opening, for upgrade purposes
-void toku_ft_update_descriptor_with_fd(FT ft, DESCRIPTOR d, int fd);
+void toku_ft_update_descriptor_with_fd(FT ft, DESCRIPTOR desc, int fd);
 void toku_ft_update_cmp_descriptor(FT ft);
 
 // get the descriptor for a ft. safe to read as long as clients honor the

ft/le-cursor.cc

@@ -101,10 +101,6 @@ PATENT RIGHTS GRANT:
 // A LE_CURSOR is good for scanning a FT from beginning to end. Useful for hot indexing.
 
 struct le_cursor {
-    // TODO: remove DBs from the ft layer comparison function 
-    // so this is never necessary
-    // use a fake db for comparisons. 
-    struct __toku_db fake_db;
     FT_CURSOR ft_cursor;
     bool neg_infinity; // true when the le cursor is positioned at -infinity (initial setting)
     bool pos_infinity; // true when the le cursor is positioned at +infinity (when _next returns DB_NOTFOUND)
@@ -124,8 +120,6 @@ toku_le_cursor_create(LE_CURSOR *le_cursor_result, FT_HANDLE ft_handle, TOKUTXN
             toku_ft_cursor_set_leaf_mode(le_cursor->ft_cursor);
             le_cursor->neg_infinity = false;
             le_cursor->pos_infinity = true;
-            // zero out the fake DB. this is a rare operation so it's not too slow.
-            memset(&le_cursor->fake_db, 0, sizeof(le_cursor->fake_db));
         }
     }
 
@@ -170,13 +164,9 @@ toku_le_cursor_is_key_greater_or_equal(LE_CURSOR le_cursor, const DBT *key) {
     } else if (le_cursor->pos_infinity) {
         result = false;     // all keys are less than +infinity
     } else {
-        // get the comparison function and descriptor from the cursor's ft
-        FT_HANDLE ft_handle = le_cursor->ft_cursor->ft_handle;
-        ft_compare_func keycompare = toku_ft_get_bt_compare(ft_handle);
-        le_cursor->fake_db.cmp_descriptor = toku_ft_get_cmp_descriptor(ft_handle);
+        FT ft = le_cursor->ft_cursor->ft_handle->ft;
         // get the current position from the cursor and compare it to the given key.
-        DBT *cursor_key = &le_cursor->ft_cursor->key;
-        int r = keycompare(&le_cursor->fake_db, cursor_key, key);
+        int r = ft->cmp(&le_cursor->ft_cursor->key, key);
         if (r <= 0) {
             result = true;  // key is right of the cursor key
         } else {

ft/node.h

@@ -88,6 +88,7 @@ PATENT RIGHTS GRANT:
 
 #pragma once
 
+#include "ft/comparator.h"
 #include "ft/cachetable.h"
 #include "ft/bndata.h"
 #include "ft/fttypes.h"
@@ -305,7 +306,7 @@ void toku_ftnode_clone_partitions(FTNODE node, FTNODE cloned_node);
 void toku_initialize_empty_ftnode(FTNODE node, BLOCKNUM blocknum, int height, int num_children, 
                                   int layout_version, unsigned int flags);
 
-int toku_ftnode_which_child(FTNODE node, const DBT *k, DESCRIPTOR desc, ft_compare_func cmp);
+int toku_ftnode_which_child(FTNODE node, const DBT *k, const toku::comparator &cmp);
 
 //
 // Field in ftnode_fetch_extra that tells the 
@@ -378,25 +379,31 @@ typedef struct ftnode_fetch_extra *FTNODE_FETCH_EXTRA;
 // TODO: put the heaviside functions into their respective 'struct .*extra;' namespaces
 //
 struct toku_msg_buffer_key_msn_heaviside_extra {
-    DESCRIPTOR desc;
-    ft_compare_func cmp;
+    const toku::comparator &cmp;
     message_buffer *msg_buffer;
     const DBT *key;
     MSN msn;
+    toku_msg_buffer_key_msn_heaviside_extra(const toku::comparator &c, message_buffer *mb, const DBT *k, MSN m) :
+        cmp(c), msg_buffer(mb), key(k), msn(m) {
+    }
 };
 int toku_msg_buffer_key_msn_heaviside(const int32_t &v, const struct toku_msg_buffer_key_msn_heaviside_extra &extra);
 
 struct toku_msg_buffer_key_msn_cmp_extra {
-    DESCRIPTOR desc;
-    ft_compare_func cmp;
+    const toku::comparator &cmp;
     message_buffer *msg_buffer;
+    toku_msg_buffer_key_msn_cmp_extra(const toku::comparator &c, message_buffer *mb) :
+        cmp(c), msg_buffer(mb) {
+    }
 };
 int toku_msg_buffer_key_msn_cmp(const struct toku_msg_buffer_key_msn_cmp_extra &extrap, const int &a, const int &b);
 
 struct toku_msg_leafval_heaviside_extra {
-    ft_compare_func compare_fun;
-    DESCRIPTOR desc;
-    DBT const * const key;
+    const toku::comparator &cmp;
+    DBT const *const key;
+    toku_msg_leafval_heaviside_extra(const toku::comparator &c, const DBT *k) :
+        cmp(c), key(k) {
+    }
 };
 int toku_msg_leafval_heaviside(DBT const &kdbt, const struct toku_msg_leafval_heaviside_extra &be);
 
@@ -404,7 +411,7 @@ unsigned int toku_bnc_nbytesinbuf(NONLEAF_CHILDINFO bnc);
 int toku_bnc_n_entries(NONLEAF_CHILDINFO bnc);
 long toku_bnc_memory_size(NONLEAF_CHILDINFO bnc);
 long toku_bnc_memory_used(NONLEAF_CHILDINFO bnc);
-void toku_bnc_insert_msg(NONLEAF_CHILDINFO bnc, const void *key, ITEMLEN keylen, const void *data, ITEMLEN datalen, enum ft_msg_type type, MSN msn, XIDS xids, bool is_fresh, DESCRIPTOR desc, ft_compare_func cmp);
+void toku_bnc_insert_msg(NONLEAF_CHILDINFO bnc, const void *key, ITEMLEN keylen, const void *data, ITEMLEN datalen, enum ft_msg_type type, MSN msn, XIDS xids, bool is_fresh, const toku::comparator &cmp);
 void toku_bnc_empty(NONLEAF_CHILDINFO bnc);
 void toku_bnc_flush_to_child(FT ft, NONLEAF_CHILDINFO bnc, FTNODE child, TXNID parent_oldest_referenced_xid_known);
 bool toku_bnc_should_promote(FT ft, NONLEAF_CHILDINFO bnc) __attribute__((const, nonnull));
@@ -435,11 +442,10 @@ enum reactivity toku_ftnode_get_leaf_reactivity(FTNODE node, uint32_t nodesize);
  * If k is equal to some pivot, then we return the next (to the right)
  * childnum.
  */
-int toku_ftnode_hot_next_child(FTNODE node, const DBT *k,
-                               DESCRIPTOR desc, ft_compare_func cmp);
+int toku_ftnode_hot_next_child(FTNODE node, const DBT *k, const toku::comparator &cmp);
 
-void toku_ftnode_put_msg(ft_compare_func compare_fun, ft_update_func update_fun,
-                         DESCRIPTOR desc, FTNODE node, int target_childnum,
+void toku_ftnode_put_msg(const toku::comparator &cmp, ft_update_func update_fun,
+                         FTNODE node, int target_childnum,
                          FT_MSG msg, bool is_fresh, txn_gc_info *gc_info,
                          size_t flow_deltas[], STAT64INFO stats_to_update);
 
@@ -447,12 +453,12 @@ void toku_ft_bn_apply_msg_once(BASEMENTNODE bn, const FT_MSG msg, uint32_t idx,
                                uint32_t le_keylen, LEAFENTRY le, txn_gc_info *gc_info,
                                uint64_t *workdonep, STAT64INFO stats_to_update);
 
-void toku_ft_bn_apply_msg(ft_compare_func compare_fun, ft_update_func update_fun,
-                          DESCRIPTOR desc, BASEMENTNODE bn, FT_MSG msg, txn_gc_info *gc_info,
+void toku_ft_bn_apply_msg(const toku::comparator &cmp, ft_update_func update_fun,
+                          BASEMENTNODE bn, FT_MSG msg, txn_gc_info *gc_info,
                           uint64_t *workdone, STAT64INFO stats_to_update);
 
-void toku_ft_leaf_apply_msg(ft_compare_func compare_fun, ft_update_func update_fun,
-                            DESCRIPTOR desc, FTNODE node, int target_childnum,
+void toku_ft_leaf_apply_msg(const toku::comparator &cmp, ft_update_func update_fun,
+                            FTNODE node, int target_childnum,
                             FT_MSG msg, txn_gc_info *gc_info,
                             uint64_t *workdone, STAT64INFO stats_to_update);
 
@@ -487,7 +493,7 @@ bool toku_ft_leaf_needs_ancestors_messages(FT ft, FTNODE node, ANCESTORS ancesto
 void toku_ft_bn_update_max_msn(FTNODE node, MSN max_msn_applied, int child_to_read);
 
 struct ft_search;
-int toku_ft_search_which_child(DESCRIPTOR desc, ft_compare_func cmp, FTNODE node, ft_search *search);
+int toku_ft_search_which_child(const toku::comparator &cmp, FTNODE node, ft_search *search);
 
 //
 // internal node inline functions

ft/tests/bnc-insert-benchmark.cc

@@ -137,6 +137,9 @@ run_test(unsigned long eltsize, unsigned long nodesize, unsigned long repeat)
     struct timeval t[2];
     gettimeofday(&t[0], NULL);
 
+    toku::comparator cmp;
+    cmp.create(long_key_cmp, nullptr);
+
     for (unsigned int i = 0; i < repeat; ++i) {
         bnc = toku_create_empty_nl();
         for (; toku_bnc_nbytesinbuf(bnc) <= nodesize; ++cur) {
@@ -144,7 +147,7 @@ run_test(unsigned long eltsize, unsigned long nodesize, unsigned long repeat)
                                 &keys[cur % 1024], sizeof keys[cur % 1024],
                                 vals[cur % 1024], eltsize - (sizeof keys[cur % 1024]),
                                 FT_NONE, next_dummymsn(), xids_123, true,
-                                NULL, long_key_cmp); assert_zero(r);
+                                cmp); assert_zero(r);
         }
         nbytesinserted += toku_bnc_nbytesinbuf(bnc);
         destroy_nonleaf_childinfo(bnc);
@@ -157,6 +160,8 @@ run_test(unsigned long eltsize, unsigned long nodesize, unsigned long repeat)
     long long unsigned eltrate = (long) (cur / dt);
     printf("%0.03lf MB/sec\n", mbrate);
     printf("%llu elts/sec\n", eltrate);
+
+    cmp.destroy();
 }
 
 int

ft/tests/comparator-test.cc

@@ -112,14 +112,16 @@ static void test_desc(void) {
     // create with d1, make sure it gets used
     cmp.create(magic_compare, &d1);
     expected_desc = &d1;
-    c = cmp.compare(&dbt_a, &dbt_b);
+    c = cmp(&dbt_a, &dbt_b);
     invariant(c == MAGIC);
 
     // set desc to d2, make sure it gets used
     cmp.set_descriptor(&d2);
     expected_desc = &d2;
-    c = cmp.compare(&dbt_a, &dbt_b);
+    c = cmp(&dbt_a, &dbt_b);
     invariant(c == MAGIC);
+
+    cmp.destroy();
 }
 
 static int dont_compare_me_bro(DB *db, const DBT *a, const DBT *b) {
@@ -137,20 +139,22 @@ static void test_infinity(void) {
     // should never be called and thus the dbt never actually read.
     DBT arbitrary_dbt;
 
-    c = cmp.compare(&arbitrary_dbt, toku_dbt_positive_infinity());
+    c = cmp(&arbitrary_dbt, toku_dbt_positive_infinity());
     invariant(c < 0);
-    c = cmp.compare(toku_dbt_negative_infinity(), &arbitrary_dbt);
+    c = cmp(toku_dbt_negative_infinity(), &arbitrary_dbt);
     invariant(c < 0);
 
-    c = cmp.compare(toku_dbt_positive_infinity(), &arbitrary_dbt);
+    c = cmp(toku_dbt_positive_infinity(), &arbitrary_dbt);
     invariant(c > 0);
-    c = cmp.compare(&arbitrary_dbt, toku_dbt_negative_infinity());
+    c = cmp(&arbitrary_dbt, toku_dbt_negative_infinity());
     invariant(c > 0);
 
-    c = cmp.compare(toku_dbt_negative_infinity(), toku_dbt_negative_infinity());
+    c = cmp(toku_dbt_negative_infinity(), toku_dbt_negative_infinity());
     invariant(c == 0);
-    c = cmp.compare(toku_dbt_positive_infinity(), toku_dbt_positive_infinity());
+    c = cmp(toku_dbt_positive_infinity(), toku_dbt_positive_infinity());
     invariant(c == 0);
+
+    cmp.destroy();
 }
 
 int main(void) {

ft/tests/ft-bfe-query.cc

@@ -103,7 +103,6 @@ int64_key_cmp (DB *db UU(), const DBT *a, const DBT *b) {
 static void
 test_prefetch_read(int fd, FT_HANDLE UU(ft), FT ft_h) {
     int r;
-    ft_h->compare_fun = int64_key_cmp;    
     FT_CURSOR XMALLOC(cursor);
     FTNODE dn = NULL;
     PAIR_ATTR attr;
@@ -250,7 +249,6 @@ test_prefetch_read(int fd, FT_HANDLE UU(ft), FT ft_h) {
 static void
 test_subset_read(int fd, FT_HANDLE UU(ft), FT ft_h) {
     int r;
-    ft_h->compare_fun = int64_key_cmp;    
     FT_CURSOR XMALLOC(cursor);
     FTNODE dn = NULL;
     FTNODE_DISK_DATA ndd = NULL;
@@ -422,6 +420,7 @@ test_prefetching(void) {
                  128*1024,
                  TOKU_DEFAULT_COMPRESSION_METHOD,
                  16);
+    ft_h->cmp.create(int64_key_cmp, nullptr);
     ft->ft = ft_h;
     toku_blocktable_create_new(&ft_h->blocktable);
     { int r_truncate = ftruncate(fd, 0); CKERR(r_truncate); }
@@ -453,6 +452,7 @@ test_prefetching(void) {
 
     toku_block_free(ft_h->blocktable, BLOCK_ALLOCATOR_TOTAL_HEADER_RESERVE);
     toku_blocktable_destroy(&ft_h->blocktable);
+    ft_h->cmp.destroy();
     toku_free(ft_h->h);
     toku_free(ft_h);
     toku_free(ft);

ft/tests/ft-clock-test.cc

@@ -147,7 +147,6 @@ static void
 test1(int fd, FT ft_h, FTNODE *dn) {
     int r;
     struct ftnode_fetch_extra bfe_all;
-    ft_h->compare_fun = string_key_cmp;
     fill_bfe_for_full_read(&bfe_all, ft_h);
     FTNODE_DISK_DATA ndd = NULL;
     r = toku_deserialize_ftnode_from(fd, make_blocknum(20), 0/*pass zero for hash*/, dn, &ndd, &bfe_all);
@@ -226,7 +225,6 @@ test2(int fd, FT ft_h, FTNODE *dn) {
     memset(&right, 0, sizeof(right));
     ft_search search;
     
-    ft_h->compare_fun = string_key_cmp;
     fill_bfe_for_subset_read(
         &bfe_subset,
         ft_h,
@@ -279,7 +277,6 @@ test3_leaf(int fd, FT ft_h, FTNODE *dn) {
     memset(&left, 0, sizeof(left));
     memset(&right, 0, sizeof(right));
     
-    ft_h->compare_fun = string_key_cmp;
     fill_bfe_for_min_read(
         &bfe_min,
         ft_h
@@ -335,13 +332,18 @@ test_serialize_nonleaf(void) {
     r = xids_create_child(xids_123, &xids_234, (TXNID)234);
     CKERR(r);
 
-    toku_bnc_insert_msg(BNC(&sn, 0), "a", 2, "aval", 5, FT_NONE, next_dummymsn(), xids_0, true, NULL, string_key_cmp);
-    toku_bnc_insert_msg(BNC(&sn, 0), "b", 2, "bval", 5, FT_NONE, next_dummymsn(), xids_123, false, NULL, string_key_cmp);
-    toku_bnc_insert_msg(BNC(&sn, 1), "x", 2, "xval", 5, FT_NONE, next_dummymsn(), xids_234, true, NULL, string_key_cmp);
+    toku::comparator cmp;
+    cmp.create(string_key_cmp, nullptr);
+
+    toku_bnc_insert_msg(BNC(&sn, 0), "a", 2, "aval", 5, FT_NONE, next_dummymsn(), xids_0, true, cmp);
+    toku_bnc_insert_msg(BNC(&sn, 0), "b", 2, "bval", 5, FT_NONE, next_dummymsn(), xids_123, false, cmp);
+    toku_bnc_insert_msg(BNC(&sn, 1), "x", 2, "xval", 5, FT_NONE, next_dummymsn(), xids_234, true, cmp);
+
     //Cleanup:
     xids_destroy(&xids_0);
     xids_destroy(&xids_123);
     xids_destroy(&xids_234);
+    cmp.destroy();
 
     FT_HANDLE XMALLOC(ft);
     FT XCALLOC(ft_h);
@@ -353,6 +355,7 @@ test_serialize_nonleaf(void) {
                  128*1024,
                  TOKU_DEFAULT_COMPRESSION_METHOD,
                  16);
+    ft_h->cmp.create(string_key_cmp, nullptr);
     ft->ft = ft_h;
     
     toku_blocktable_create_new(&ft_h->blocktable);
@@ -387,6 +390,7 @@ test_serialize_nonleaf(void) {
     toku_block_free(ft_h->blocktable, BLOCK_ALLOCATOR_TOTAL_HEADER_RESERVE);
     toku_blocktable_destroy(&ft_h->blocktable);
     toku_free(ft_h->h);
+    ft_h->cmp.destroy();
     toku_free(ft_h);
     toku_free(ft);
 

ft/tests/ft-serialize-benchmark.cc

@@ -195,9 +195,9 @@ test_serialize_leaf(int valsize, int nelts, double entropy, int ser_runs, int de
                  128*1024,
                  TOKU_DEFAULT_COMPRESSION_METHOD,
                  16);
+    ft_h->cmp.create(long_key_cmp, nullptr);
     ft->ft = ft_h;
     
-    ft_h->compare_fun = long_key_cmp;
     toku_blocktable_create_new(&ft_h->blocktable);
     { int r_truncate = ftruncate(fd, 0); CKERR(r_truncate); }
     //Want to use block #20
@@ -279,6 +279,7 @@ test_serialize_leaf(int valsize, int nelts, double entropy, int ser_runs, int de
 
     toku_block_free(ft_h->blocktable, BLOCK_ALLOCATOR_TOTAL_HEADER_RESERVE);
     toku_blocktable_destroy(&ft_h->blocktable);
+    ft_h->cmp.destroy();
     toku_free(ft_h->h);
     toku_free(ft_h);
     toku_free(ft);
@@ -317,6 +318,8 @@ test_serialize_nonleaf(int valsize, int nelts, double entropy, int ser_runs, int
     XIDS xids_123;
     r = xids_create_child(xids_0, &xids_123, (TXNID)123);
     CKERR(r);
+    toku::comparator cmp;
+    cmp.create(long_key_cmp, nullptr);
     int nperchild = nelts / 8;
     for (int ck = 0; ck < sn.n_children; ++ck) {
         long k;
@@ -332,7 +335,7 @@ test_serialize_nonleaf(int valsize, int nelts, double entropy, int ser_runs, int
             }
             memset(&buf[c], 0, valsize - c);
 
-            toku_bnc_insert_msg(bnc, &k, sizeof k, buf, valsize, FT_NONE, next_dummymsn(), xids_123, true, NULL, long_key_cmp);
+            toku_bnc_insert_msg(bnc, &k, sizeof k, buf, valsize, FT_NONE, next_dummymsn(), xids_123, true, cmp);
         }
         if (ck < 7) {
             DBT pivotkey;
@@ -343,6 +346,7 @@ test_serialize_nonleaf(int valsize, int nelts, double entropy, int ser_runs, int
     //Cleanup:
     xids_destroy(&xids_0);
     xids_destroy(&xids_123);
+    cmp.destroy();
 
     FT_HANDLE XMALLOC(ft);
     FT XCALLOC(ft_h);
@@ -354,9 +358,9 @@ test_serialize_nonleaf(int valsize, int nelts, double entropy, int ser_runs, int
                  128*1024,
                  TOKU_DEFAULT_COMPRESSION_METHOD,
                  16);
+    ft_h->cmp.create(long_key_cmp, nullptr);
     ft->ft = ft_h;
     
-    ft_h->compare_fun = long_key_cmp;
     toku_blocktable_create_new(&ft_h->blocktable);
     { int r_truncate = ftruncate(fd, 0); CKERR(r_truncate); }
     //Want to use block #20
@@ -411,10 +415,12 @@ test_serialize_nonleaf(int valsize, int nelts, double entropy, int ser_runs, int
     toku_block_free(ft_h->blocktable, BLOCK_ALLOCATOR_TOTAL_HEADER_RESERVE);
     toku_blocktable_destroy(&ft_h->blocktable);
     toku_free(ft_h->h);
+    ft_h->cmp.destroy();
     toku_free(ft_h);
     toku_free(ft);
     toku_free(ndd);
     toku_free(ndd2);
+    cmp.destroy();
 
     r = close(fd); assert(r != -1);
 }

ft/tests/ft-serialize-test.cc

@@ -164,7 +164,6 @@ string_key_cmp(DB *UU(e), const DBT *a, const DBT *b)
 static void
 setup_dn(enum ftnode_verify_type bft, int fd, FT ft_h, FTNODE *dn, FTNODE_DISK_DATA* ndd) {
     int r;
-    ft_h->compare_fun = string_key_cmp;
     if (bft == read_all) {
         struct ftnode_fetch_extra bfe;
         fill_bfe_for_full_read(&bfe, ft_h);
@@ -1050,13 +1049,18 @@ test_serialize_nonleaf(enum ftnode_verify_type bft, bool do_clone) {
     r = xids_create_child(xids_123, &xids_234, (TXNID)234);
     CKERR(r);
 
-    toku_bnc_insert_msg(BNC(&sn, 0), "a", 2, "aval", 5, FT_NONE, next_dummymsn(), xids_0, true, NULL, string_key_cmp);
-    toku_bnc_insert_msg(BNC(&sn, 0), "b", 2, "bval", 5, FT_NONE, next_dummymsn(), xids_123, false, NULL, string_key_cmp);
-    toku_bnc_insert_msg(BNC(&sn, 1), "x", 2, "xval", 5, FT_NONE, next_dummymsn(), xids_234, true, NULL, string_key_cmp);
+    toku::comparator cmp;
+    cmp.create(string_key_cmp, nullptr);
+
+    toku_bnc_insert_msg(BNC(&sn, 0), "a", 2, "aval", 5, FT_NONE, next_dummymsn(), xids_0, true, cmp);
+    toku_bnc_insert_msg(BNC(&sn, 0), "b", 2, "bval", 5, FT_NONE, next_dummymsn(), xids_123, false, cmp);
+    toku_bnc_insert_msg(BNC(&sn, 1), "x", 2, "xval", 5, FT_NONE, next_dummymsn(), xids_234, true, cmp);
+
     //Cleanup:
     xids_destroy(&xids_0);
     xids_destroy(&xids_123);
     xids_destroy(&xids_234);
+    cmp.destroy();
 
     FT_HANDLE XMALLOC(ft);
     FT XCALLOC(ft_h);
@@ -1068,6 +1072,7 @@ test_serialize_nonleaf(enum ftnode_verify_type bft, bool do_clone) {
                  128*1024,
                  TOKU_DEFAULT_COMPRESSION_METHOD,
                  16);
+    ft_h->cmp.create(string_key_cmp, nullptr);
     ft->ft = ft_h;
     
     toku_blocktable_create_new(&ft_h->blocktable);
@@ -1125,6 +1130,7 @@ test_serialize_nonleaf(enum ftnode_verify_type bft, bool do_clone) {
     toku_free(ft);
     toku_free(src_ndd);
     toku_free(dest_ndd);
+    cmp.destroy();
 
     r = close(fd); assert(r != -1);
 }

ft/tests/make-tree.cc

@@ -152,7 +152,7 @@ insert_into_child_buffer(FT_HANDLE ft, FTNODE node, int childnum, int minkey, in
         unsigned int key = htonl(val);
         DBT thekey; toku_fill_dbt(&thekey, &key, sizeof key);
         DBT theval; toku_fill_dbt(&theval, &val, sizeof val);
-        toku_ft_append_to_child_buffer(ft->ft->compare_fun, NULL, node, childnum, FT_INSERT, msn, xids_get_root_xids(), true, &thekey, &theval);
+        toku_ft_append_to_child_buffer(ft->ft->cmp, node, childnum, FT_INSERT, msn, xids_get_root_xids(), true, &thekey, &theval);
 	node->max_msn_applied_to_node_on_disk = msn;
     }
 }

ft/tests/msnfilter.cc

@@ -134,7 +134,7 @@ append_leaf(FT_HANDLE ft, FTNODE leafnode, void *key, uint32_t keylen, void *val
     FT_MSG_S msg = { FT_INSERT, msn, xids_get_root_xids(), .u={.id = { &thekey, &theval }} };
     txn_gc_info gc_info(nullptr, TXNID_NONE, TXNID_NONE, false);
 
-    toku_ft_leaf_apply_msg(ft->ft->compare_fun, ft->ft->update_fun, &ft->ft->cmp_descriptor, leafnode, -1, &msg, &gc_info, nullptr, nullptr);
+    toku_ft_leaf_apply_msg(ft->ft->cmp, ft->ft->update_fun, leafnode, -1, &msg, &gc_info, nullptr, nullptr);
     {
 	int r = toku_ft_lookup(ft, &thekey, lookup_checkf, &pair);
 	assert(r==0);
@@ -142,7 +142,7 @@ append_leaf(FT_HANDLE ft, FTNODE leafnode, void *key, uint32_t keylen, void *val
     }
 
     FT_MSG_S badmsg = { FT_INSERT, msn, xids_get_root_xids(), .u={.id = { &thekey, &badval }} };
-    toku_ft_leaf_apply_msg(ft->ft->compare_fun, ft->ft->update_fun, &ft->ft->cmp_descriptor, leafnode, -1, &badmsg, &gc_info, nullptr, nullptr);
+    toku_ft_leaf_apply_msg(ft->ft->cmp, ft->ft->update_fun, leafnode, -1, &badmsg, &gc_info, nullptr, nullptr);
 
     // message should be rejected for duplicate msn, row should still have original val
     {
@@ -155,7 +155,7 @@ append_leaf(FT_HANDLE ft, FTNODE leafnode, void *key, uint32_t keylen, void *val
     msn = next_dummymsn();
     ft->ft->h->max_msn_in_ft = msn;
     FT_MSG_S msg2 = { FT_INSERT, msn, xids_get_root_xids(), .u={.id = { &thekey, &val2 }} };
-    toku_ft_leaf_apply_msg(ft->ft->compare_fun, ft->ft->update_fun, &ft->ft->cmp_descriptor, leafnode, -1, &msg2, &gc_info, nullptr, nullptr);
+    toku_ft_leaf_apply_msg(ft->ft->cmp, ft->ft->update_fun, leafnode, -1, &msg2, &gc_info, nullptr, nullptr);
 
     // message should be accepted, val should have new value
     {
@@ -167,7 +167,7 @@ append_leaf(FT_HANDLE ft, FTNODE leafnode, void *key, uint32_t keylen, void *val
     // now verify that message with lesser (older) msn is rejected
     msn.msn = msn.msn - 10;
     FT_MSG_S msg3 = { FT_INSERT, msn, xids_get_root_xids(), .u={.id = { &thekey, &badval } }};
-    toku_ft_leaf_apply_msg(ft->ft->compare_fun, ft->ft->update_fun, &ft->ft->cmp_descriptor, leafnode, -1, &msg3, &gc_info, nullptr, nullptr);
+    toku_ft_leaf_apply_msg(ft->ft->cmp, ft->ft->update_fun, leafnode, -1, &msg3, &gc_info, nullptr, nullptr);
 
     // message should be rejected, val should still have value in pair2
     {

ft/tests/verify-bad-msn.cc

@@ -156,7 +156,7 @@ insert_into_child_buffer(FT_HANDLE ft, FTNODE node, int childnum, int minkey, in
         unsigned int key = htonl(val);
         DBT thekey; toku_fill_dbt(&thekey, &key, sizeof key);
         DBT theval; toku_fill_dbt(&theval, &val, sizeof val);
-        toku_ft_append_to_child_buffer(ft->ft->compare_fun, NULL, node, childnum, FT_INSERT, msn, xids_get_root_xids(), true, &thekey, &theval);
+        toku_ft_append_to_child_buffer(ft->ft->cmp, node, childnum, FT_INSERT, msn, xids_get_root_xids(), true, &thekey, &theval);
 
 	// Create bad tree (don't do following):
 	// node->max_msn_applied_to_node = msn;

ft/tests/verify-misrouted-msgs.cc

@@ -144,7 +144,7 @@ insert_into_child_buffer(FT_HANDLE ft, FTNODE node, int childnum, int minkey, in
         DBT thekey; toku_fill_dbt(&thekey, &key, sizeof key);
         DBT theval; toku_fill_dbt(&theval, &val, sizeof val);
 	MSN msn = next_dummymsn();
-        toku_ft_append_to_child_buffer(ft->ft->compare_fun, NULL, node, childnum, FT_INSERT, msn, xids_get_root_xids(), true, &thekey, &theval);
+        toku_ft_append_to_child_buffer(ft->ft->cmp, node, childnum, FT_INSERT, msn, xids_get_root_xids(), true, &thekey, &theval);
     }
 }
 

ft/valgrind.suppressions

@@ -281,3 +281,16 @@
    fun:_dl_start
    obj:/lib/x86_64-linux-gnu/ld-2.17.so
 }
+{
+    <ld_is_not_clean_on_arch_linux_june_2014>
+    Memcheck:Leak
+    match-leak-kinds: reachable
+    fun:calloc
+    obj:/usr/lib/libdl-2.19.so
+    fun:dlsym
+    fun:_Z19toku_memory_startupv
+    fun:call_init.part.0
+    fun:_dl_init
+    obj:/usr/lib/ld-2.19.so
+}
+

locktree/concurrent_tree.cc

@@ -91,7 +91,7 @@ PATENT RIGHTS GRANT:
 
 #include <toku_assert.h>
 
-void concurrent_tree::create(comparator *cmp) {
+void concurrent_tree::create(const comparator *cmp) {
     // start with an empty root node. we do this instead of
     // setting m_root to null so there's always a root to lock
     m_root.create_root(cmp);

locktree/concurrent_tree.h

@@ -173,7 +173,7 @@ public:
     };
 
     // effect: initialize the tree to an empty state
-    void create(comparator *cmp);
+    void create(const comparator *cmp);
 
     // effect: destroy the tree.
     // requires: tree is empty

locktree/keyrange.cc

@@ -129,13 +129,13 @@ void keyrange::create_copy(const keyrange &range) {
 // extend this keyrange by choosing the leftmost and rightmost
 // endpoints between this range and the given. replaced keys
 // in this range are freed and inherited keys are copied.
-void keyrange::extend(comparator *cmp, const keyrange &range) {
+void keyrange::extend(const comparator &cmp, const keyrange &range) {
     const DBT *range_left = range.get_left_key();
     const DBT *range_right = range.get_right_key();
-    if (cmp->compare(range_left, get_left_key()) < 0) {
+    if (cmp(range_left, get_left_key()) < 0) {
         replace_left_key(range_left);
     }
-    if (cmp->compare(range_right, get_right_key()) > 0) {
+    if (cmp(range_right, get_right_key()) > 0) {
         replace_right_key(range_right);
     }
 }
@@ -152,20 +152,20 @@ uint64_t keyrange::get_memory_size(void) const {
 }
 
 // compare ranges.
-keyrange::comparison keyrange::compare(comparator *cmp, const keyrange &range) const {
-    if (cmp->compare(get_right_key(), range.get_left_key()) < 0) {
+keyrange::comparison keyrange::compare(const comparator &cmp, const keyrange &range) const {
+    if (cmp(get_right_key(), range.get_left_key()) < 0) {
         return comparison::LESS_THAN;
-    } else if (cmp->compare(get_left_key(), range.get_right_key()) > 0) {
+    } else if (cmp(get_left_key(), range.get_right_key()) > 0) {
         return comparison::GREATER_THAN;
-    } else if (cmp->compare(get_left_key(), range.get_left_key()) == 0 &&
-            cmp->compare(get_right_key(), range.get_right_key()) == 0) {
+    } else if (cmp(get_left_key(), range.get_left_key()) == 0 &&
+            cmp(get_right_key(), range.get_right_key()) == 0) {
         return comparison::EQUALS;
     } else {
         return comparison::OVERLAPS;
     }
 }
 
-bool keyrange::overlaps(comparator *cmp, const keyrange &range) const {
+bool keyrange::overlaps(const comparator &cmp, const keyrange &range) const {
     // equality is a stronger form of overlapping.
     // so two ranges "overlap" if they're either equal or just overlapping.
     comparison c = compare(cmp, range);

locktree/keyrange.h

@@ -117,7 +117,7 @@ public:
     // effect: extends the keyrange by choosing the leftmost and rightmost
     //         endpoints from this range and the given range.
     //         replaced keys in this range are freed, new keys are copied.
-    void extend(comparator *cmp, const keyrange &range);
+    void extend(const comparator &cmp, const keyrange &range);
 
     // returns: the amount of memory this keyrange takes. does not account
     //          for point optimizations or malloc overhead.
@@ -143,10 +143,10 @@ public:
     //          EQUALS       if given range has the same left and right endpoints
     //          OVERLAPS     if at least one of the given range's endpoints falls
     //                       between this range's endpoints
-    comparison compare(comparator *cmp, const keyrange &range) const;
+    comparison compare(const comparator &cmp, const keyrange &range) const;
 
     // returns: true if the range and the given range are equal or overlapping
-    bool overlaps(comparator *cmp, const keyrange &range) const;
+    bool overlaps(const comparator &cmp, const keyrange &range) const;
 
     // returns: a keyrange representing -inf, +inf
     static keyrange get_infinite_range(void);

locktree/locktree.cc

@@ -121,14 +121,12 @@ void locktree::create(locktree_manager *mgr, DICTIONARY_ID dict_id,
     m_mgr = mgr;
     m_dict_id = dict_id;
 
-    // the only reason m_cmp is malloc'd here is to prevent gdb from printing
-    // out an entire DB struct every time you inspect a locktree.
-    XCALLOC(m_cmp);
-    m_cmp->create(cmp, desc);
+    m_cmp.create(cmp, desc);
     m_reference_count = 1;
     m_userdata = nullptr;
+
     XCALLOC(m_rangetree);
-    m_rangetree->create(m_cmp);
+    m_rangetree->create(&m_cmp);
 
     m_sto_txnid = TXNID_NONE;
     m_sto_buffer.create();
@@ -155,11 +153,10 @@ void locktree::create(locktree_manager *mgr, DICTIONARY_ID dict_id,
 
 void locktree::destroy(void) {
     invariant(m_reference_count == 0);
+    m_cmp.destroy();
     m_rangetree->destroy();
-    toku_free(m_cmp);
     toku_free(m_rangetree);
     m_sto_buffer.destroy();
-
     m_lock_request_info.pending_lock_requests.destroy();
 }
 
@@ -299,7 +296,7 @@ void locktree::sto_migrate_buffer_ranges_to_tree(void *prepared_lkr) {
 
     concurrent_tree sto_rangetree;
     concurrent_tree::locked_keyrange sto_lkr;
-    sto_rangetree.create(m_cmp);
+    sto_rangetree.create(&m_cmp);
 
     // insert all of the ranges from the single txnid buffer into a new rangtree
     range_buffer::iterator iter(&m_sto_buffer);
@@ -438,7 +435,7 @@ int locktree::try_acquire_lock(bool is_write_request,
                                txnid_set *conflicts, bool big_txn) {
     // All ranges in the locktree must have left endpoints <= right endpoints.
     // Range comparisons rely on this fact, so we make a paranoid invariant here.
-    paranoid_invariant(m_cmp->compare(left_key, right_key) <= 0);
+    paranoid_invariant(m_cmp(left_key, right_key) <= 0);
     int r = m_mgr == nullptr ? 0 :
             m_mgr->check_current_lock_constraints(big_txn);
     if (r == 0) {
@@ -581,7 +578,7 @@ void locktree::release_locks(TXNID txnid, const range_buffer *ranges) {
             const DBT *right_key = rec.get_right_key();
             // All ranges in the locktree must have left endpoints <= right endpoints.
             // Range comparisons rely on this fact, so we make a paranoid invariant here.
-            paranoid_invariant(m_cmp->compare(left_key, right_key) <= 0);
+            paranoid_invariant(m_cmp(left_key, right_key) <= 0);
             remove_overlapping_locks_for_txnid(txnid, left_key, right_key);
             iter.next();
         }
@@ -795,7 +792,7 @@ struct lt_lock_request_info *locktree::get_lock_request_info(void) {
 }
 
 void locktree::set_descriptor(DESCRIPTOR desc) {
-    m_cmp->set_descriptor(desc);
+    m_cmp.set_descriptor(desc);
 }
 
 locktree_manager *locktree::get_manager(void) const {

locktree/locktree.h

@@ -323,8 +323,7 @@ namespace toku {
     // - Destroy the manager.
     class locktree {
     public:
-        // effect: Creates a locktree that uses the given memory tracker
-        //         to report memory usage and honor memory constraints.
+        // effect: Creates a locktree
         void create(locktree_manager *mgr, DICTIONARY_ID dict_id,
                     DESCRIPTOR desc, ft_compare_func cmp);
 
@@ -399,7 +398,7 @@ namespace toku {
         // is valid for as long as the locktree. this is currently
         // implemented by opening an ft_handle for this locktree and
         // storing it as userdata below.
-        comparator *m_cmp;
+        comparator m_cmp;
 
         concurrent_tree *m_rangetree;
 

locktree/tests/concurrent_tree_lkr_acquire_release.cc

@@ -126,19 +126,19 @@ void concurrent_tree_unit_test::test_lkr_acquire_release(void) {
 
             // if the subtree root does not overlap then one of its children
             // must exist and have an overlapping range.
-            if (!lkr.m_subtree->m_range.overlaps(&cmp, range)) {
+            if (!lkr.m_subtree->m_range.overlaps(cmp, range)) {
                 treenode *left = lkr.m_subtree->m_left_child.ptr;
                 treenode *right = lkr.m_subtree->m_right_child.ptr;
                 if (left != nullptr) {
                     // left exists, so if it does not overlap then the right must
-                    if (!left->m_range.overlaps(&cmp, range)) {
+                    if (!left->m_range.overlaps(cmp, range)) {
                         invariant_notnull(right);
-                        invariant(right->m_range.overlaps(&cmp, range));
+                        invariant(right->m_range.overlaps(cmp, range));
                     }
                 } else {
                     // no left child, so the right must exist and be overlapping
                     invariant_notnull(right);
-                    invariant(right->m_range.overlaps(&cmp, range));
+                    invariant(right->m_range.overlaps(cmp, range));
                 }
             }
 
@@ -160,6 +160,8 @@ void concurrent_tree_unit_test::test_lkr_acquire_release(void) {
         lkr.release();
         tree.destroy();
     }
+
+    cmp.destroy();
 }
 
 } /* namespace toku */

locktree/tests/concurrent_tree_lkr_insert_remove.cc

@@ -117,17 +117,17 @@ static void verify_unique_keys(void) {
 }
 
 static uint64_t check_for_range_and_count(concurrent_tree::locked_keyrange *lkr,
-        comparator *cmp, const keyrange &range, bool range_should_exist) {
+        const comparator &cmp, const keyrange &range, bool range_should_exist) {
 
     struct check_fn_obj {
-        comparator *cmp;
+        const comparator *cmp;
         uint64_t count;
         keyrange target_range;
         bool target_range_found;
 
         bool fn(const keyrange &query_range, TXNID txnid) { 
             (void) txnid;
-            if (query_range.compare(cmp, target_range) == keyrange::comparison::EQUALS) {
+            if (query_range.compare(*cmp, target_range) == keyrange::comparison::EQUALS) {
                 invariant(!target_range_found);
                 target_range_found = true;
             }
@@ -135,7 +135,7 @@ static uint64_t check_for_range_and_count(concurrent_tree::locked_keyrange *lkr,
             return true;
         }
     } check_fn;
-    check_fn.cmp = cmp;
+    check_fn.cmp = &cmp;
     check_fn.count = 0;
     check_fn.target_range = range;
     check_fn.target_range_found = false;
@@ -174,14 +174,14 @@ void concurrent_tree_unit_test::test_lkr_insert_remove(void) {
         // insert an element. it should exist and the
         // count should be correct.
         lkr.insert(range, i);
-        n = check_for_range_and_count(&lkr, &cmp, range, true);
+        n = check_for_range_and_count(&lkr, cmp, range, true);
         if (i >= cap) {
             invariant(n == cap + 1);
             // remove an element previously inserted. it should
             // no longer exist and the count should be correct.
             range.create(get_ith_key_from_set(i - cap), get_ith_key_from_set(i - cap));
             lkr.remove(range);
-            n = check_for_range_and_count(&lkr, &cmp, range, false);
+            n = check_for_range_and_count(&lkr, cmp, range, false);
             invariant(n == cap);
         } else {
             invariant(n == i + 1);
@@ -193,12 +193,13 @@ void concurrent_tree_unit_test::test_lkr_insert_remove(void) {
         keyrange range;
         range.create(get_ith_key_from_set(num_keys - i - 1), get_ith_key_from_set(num_keys - i - 1));
         lkr.remove(range);
-        n = check_for_range_and_count(&lkr, &cmp, range, false);
+        n = check_for_range_and_count(&lkr, cmp, range, false);
         invariant(n == (cap - i - 1));
     }
 
     lkr.release();
     tree.destroy();
+    cmp.destroy();
 }
 
 } /* namespace toku */

locktree/tests/concurrent_tree_lkr_insert_serial_large.cc

@@ -136,6 +136,7 @@ void concurrent_tree_unit_test::test_lkr_insert_serial_large(void) {
 
     lkr.release();
     tree.destroy();
+    cmp.destroy();
 }
 
 } /* namespace toku */

locktree/tests/concurrent_tree_lkr_remove_all.cc

@@ -132,6 +132,8 @@ void concurrent_tree_unit_test::test_lkr_remove_all(void) {
         lkr.release();
         tree.destroy();
     }
+
+    cmp.destroy();
 }
 
 } /* namespace toku */

locktree/tests/locktree_misc.cc

@@ -128,11 +128,11 @@ void locktree_unit_test::test_misc(void) {
     // descriptor when we set the locktree's descriptor
     lt.set_descriptor(&d1);
     expected_descriptor = &d1;
-    r = lt.m_cmp->compare(&dbt_a, &dbt_b);
+    r = lt.m_cmp(&dbt_a, &dbt_b);
     invariant(r == expected_comparison_magic);
     lt.set_descriptor(&d2);
     expected_descriptor = &d2;
-    r = lt.m_cmp->compare(&dbt_a, &dbt_b);
+    r = lt.m_cmp(&dbt_a, &dbt_b);
     invariant(r == expected_comparison_magic);
 
     lt.release_reference();

locktree/tests/locktree_overlapping_relock.cc

@@ -143,7 +143,7 @@ void locktree_unit_test::test_overlapping_relock(void) {
             bool saw_the_other;
             TXNID expected_txnid;
             keyrange *expected_range;
-            comparator *cmp;
+            const comparator *cmp;
             bool fn(const keyrange &range, TXNID txnid) {
                 if (txnid == the_other_txnid) {
                     invariant(!saw_the_other);
@@ -151,12 +151,12 @@ void locktree_unit_test::test_overlapping_relock(void) {
                     return true;
                 }
                 invariant(txnid == expected_txnid);
-                keyrange::comparison c = range.compare(cmp, *expected_range);
+                keyrange::comparison c = range.compare(*cmp, *expected_range);
                 invariant(c == keyrange::comparison::EQUALS);
                 return true;
             }
         } verify_fn;
-        verify_fn.cmp = lt.m_cmp;
+        verify_fn.cmp = &lt.m_cmp;
 
 #define do_verify() \
         do { verify_fn.saw_the_other = false; locktree_iterate<verify_fn_obj>(&lt, &verify_fn); } while (0)

locktree/tests/locktree_single_txnid_optimization.cc

@@ -149,15 +149,15 @@ void locktree_unit_test::test_single_txnid_optimization(void) {
             struct verify_fn_obj {
                 TXNID expected_txnid;
                 keyrange *expected_range;
-                comparator *cmp;
+                const comparator *cmp;
                 bool fn(const keyrange &range, TXNID txnid) {
                     invariant(txnid == expected_txnid);
-                    keyrange::comparison c = range.compare(cmp, *expected_range);
+                    keyrange::comparison c = range.compare(*cmp, *expected_range);
                     invariant(c == keyrange::comparison::EQUALS);
                     return true;
                 }
             } verify_fn;
-            verify_fn.cmp = lt.m_cmp;
+            verify_fn.cmp = &lt.m_cmp;
 
             keyrange range;
             range.create(one, one);

locktree/treenode.cc

@@ -99,7 +99,7 @@ void treenode::mutex_unlock(void) {
     toku_mutex_unlock(&m_mutex);
 }
 
-void treenode::init(comparator *cmp) {
+void treenode::init(const comparator *cmp) {
     m_txnid = TXNID_NONE;
     m_is_root = false;
     m_is_empty = true;
@@ -117,7 +117,7 @@ void treenode::init(comparator *cmp) {
     m_right_child.set(nullptr);
 }
 
-void treenode::create_root(comparator *cmp) {
+void treenode::create_root(const comparator *cmp) {
     init(cmp);
     m_is_root = true;
 }
@@ -145,10 +145,10 @@ bool treenode::is_empty(void) {
 }
 
 bool treenode::range_overlaps(const keyrange &range) {
-    return m_range.overlaps(m_cmp, range);
+    return m_range.overlaps(*m_cmp, range);
 }
 
-treenode *treenode::alloc(comparator *cmp, const keyrange &range, TXNID txnid) {
+treenode *treenode::alloc(const comparator *cmp, const keyrange &range, TXNID txnid) {
     treenode *XCALLOC(node);
     node->init(cmp);
     node->set_range_and_txnid(range, txnid);
@@ -190,7 +190,7 @@ treenode *treenode::find_node_with_overlapping_child(const keyrange &range,
 
     // determine which child to look at based on a comparison. if we were
     // given a comparison hint, use that. otherwise, compare them now.
-    keyrange::comparison c = cmp_hint ? *cmp_hint : range.compare(m_cmp, m_range);
+    keyrange::comparison c = cmp_hint ? *cmp_hint : range.compare(*m_cmp, m_range);
 
     treenode *child;
     if (c == keyrange::comparison::LESS_THAN) {
@@ -209,7 +209,7 @@ treenode *treenode::find_node_with_overlapping_child(const keyrange &range,
     if (child == nullptr) {
         return this;
     } else {
-        c = range.compare(m_cmp, child->m_range);
+        c = range.compare(*m_cmp, child->m_range);
         if (c == keyrange::comparison::EQUALS || c == keyrange::comparison::OVERLAPS) {
             child->mutex_unlock();
             return this;
@@ -225,7 +225,7 @@ treenode *treenode::find_node_with_overlapping_child(const keyrange &range,
 
 template <class F>
 void treenode::traverse_overlaps(const keyrange &range, F *function) {
-    keyrange::comparison c = range.compare(m_cmp, m_range);
+    keyrange::comparison c = range.compare(*m_cmp, m_range);
     if (c == keyrange::comparison::EQUALS) {
         // Doesn't matter if fn wants to keep going, there
         // is nothing left, so return.
@@ -264,7 +264,7 @@ void treenode::traverse_overlaps(const keyrange &range, F *function) {
 void treenode::insert(const keyrange &range, TXNID txnid) {
     // choose a child to check. if that child is null, then insert the new node there.
     // otherwise recur down that child's subtree
-    keyrange::comparison c = range.compare(m_cmp, m_range);
+    keyrange::comparison c = range.compare(*m_cmp, m_range);
     if (c == keyrange::comparison::LESS_THAN) {
         treenode *left_child = lock_and_rebalance_left();
         if (left_child == nullptr) {
@@ -382,7 +382,7 @@ treenode *treenode::remove(const keyrange &range) {
     // if the range is equal to this node's range, then just remove
     // the root of this subtree. otherwise search down the tree
     // in either the left or right children.
-    keyrange::comparison c = range.compare(m_cmp, m_range);
+    keyrange::comparison c = range.compare(*m_cmp, m_range);
     switch (c) {
     case keyrange::comparison::EQUALS:
         return remove_root_of_subtree();

locktree/treenode.h

@@ -123,7 +123,7 @@ public:
     // - node may be unlocked if no other thread has visibility
 
     // effect: create the root node
-    void create_root(comparator *cmp);
+    void create_root(const comparator *cmp);
 
     // effect: destroys the root node
     void destroy_root(void);
@@ -210,7 +210,7 @@ private:
     child_ptr m_right_child;
 
     // comparator for ranges
-    comparator *m_cmp;
+    const comparator *m_cmp;
 
     // marked for the root node. the root node is never free()'d
     // when removed, but instead marked as empty.
@@ -220,7 +220,7 @@ private:
     bool m_is_empty;
 
     // effect: initializes an empty node with the given comparator
-    void init(comparator *cmp);
+    void init(const comparator *cmp);
 
     // requires: *parent is initialized to something meaningful.
     // requires: subtree is non-empty
@@ -267,7 +267,7 @@ private:
     treenode *maybe_rebalance(void);
 
     // returns: allocated treenode populated with a copy of the range and txnid
-    static treenode *alloc(comparator *cmp, const keyrange &range, TXNID txnid);
+    static treenode *alloc(const comparator *cmp, const keyrange &range, TXNID txnid);
 
     // requires: node is a locked root node, or an unlocked non-root node
     static void free(treenode *node);