diff --git a/src/lladd/page/slotted.c b/src/lladd/page/slotted.c
index bb982a6..3afb4dc 100644
--- a/src/lladd/page/slotted.c
+++ b/src/lladd/page/slotted.c
@@ -2,12 +2,126 @@
 
 
 #include "../page.h"
-//#include "../blobManager.h"  /** So that we can call sizeof(blob_record_t) */
 #include "slotted.h"
 #include <assert.h>
 
 static void really_do_ralloc(Page * page, recordid rid) ;
 size_t slottedFreespaceForSlot(Page * page, int slot);
+
+void fsckSlottedPage(const Page const * page) {
+
+#ifndef SLOTTED_PAGE_SKIP_SANITY_CHECKS
+  Page dummy;
+
+  dummy.id = -1;
+  dummy.memAddr = 0;
+
+  const short page_type = *page_type_ptr(page);
+  const short numslots  = *numslots_ptr(page);
+  const short freespace = *freespace_ptr(page);
+  const short freelist  = *freelist_ptr(page);
+
+  const long slotListStart = (long)slot_length_ptr(&dummy, numslots-1);
+  assert(slotListStart < PAGE_SIZE && slotListStart >= 0);
+  assert(page_type == SLOTTED_PAGE || 
+	 page_type == BOUNDARY_TAG_PAGE);
+  assert(numslots >= 0);
+  assert(numslots * SLOTTED_PAGE_OVERHEAD_PER_RECORD < PAGE_SIZE);
+  assert(freespace >= 0);
+  assert(freespace <= slotListStart);
+  assert(freelist >= INVALID_SLOT);
+  assert(freelist < numslots);
+  
+  // Now, check integrity of freelist.  All free slots less than numslots should be on it, in order.  
+
+  short * slot_offsets = alloca(numslots * sizeof(short));
+  short * slot_lengths = alloca(numslots * sizeof(short));
+  for(int i = 0; i < numslots; i++) { 
+    slot_offsets[i] = *slot_ptr(page, i);
+    slot_lengths[i] = *slot_length_ptr(page, i);
+  }
+
+  short foundEndOfList = 0;
+
+  if(freelist != INVALID_SLOT) {
+    assert(slot_offsets[freelist] == INVALID_SLOT);
+  } else { 
+    foundEndOfList = 1;
+  }
+
+  for(short i = 0; i < numslots; i++) { 
+    const short slot_length = slot_lengths[i];
+    const short slot_offset = slot_offsets[i];
+    if(slot_offset == INVALID_SLOT) {
+      /*      if(last_freeslot == INVALID_SLOT) { 
+	assert(freelist == i);
+      } else {
+	assert(last_freeslot_length == i);
+      }
+      last_freeslot = i;
+      last_freeslot_length = slot_length; */
+      if(slot_length == INVALID_SLOT) { 
+	assert(!foundEndOfList);
+	foundEndOfList = 1;  
+      } else {
+	assert (slot_offsets[slot_length] == INVALID_SLOT);
+      }
+    } else { 
+      assert(slot_offset + slot_length <= freespace);
+    }
+  }
+
+  // Is the free list terminated?
+  assert(foundEndOfList);
+
+#ifdef SLOTTED_PAGE_CHECK_FOR_OVERLAP
+
+  const byte UNUSED = 0xFF;
+  const byte PAGE_HEADER = 0xFE;
+  const byte SLOTTED_HEADER = 0xFD;
+  //  const byte SLOT_LIST = 0xFC;
+  const byte FREE_SPACE = 0xFB;
+
+  const unsigned short S_SLOT_LIST = 0xFCFC;
+
+  byte image[PAGE_SIZE];
+  for(short i = 0; i < PAGE_SIZE; i++) { 
+    image[i] = UNUSED;
+  }
+  for(short i = USABLE_SIZE_OF_PAGE; i < PAGE_SIZE; i++) {
+    image[i] = PAGE_HEADER;
+  }
+  for(short i = USABLE_SIZE_OF_PAGE - SLOTTED_PAGE_HEADER_OVERHEAD; i < USABLE_SIZE_OF_PAGE; i++) { 
+    image[i] = SLOTTED_HEADER;
+  }
+  for(short i = *freespace_ptr(page); i < slotListStart; i++) { 
+    image[i] = FREE_SPACE;
+  }
+
+  dummy.memAddr = image;
+
+  for(short i = 0; i < *numslots_ptr(page); i++) { 
+    *slot_ptr(&dummy, i) = S_SLOT_LIST;
+    *slot_length_ptr(&dummy, i) = S_SLOT_LIST;
+  }
+  for(short i = 0; i < *numslots_ptr(page); i++) { 
+    short slot_offset = *slot_ptr(page, i);
+    if(slot_offset != INVALID_SLOT) { 
+      const unsigned char ci = i % 0xFF;
+      short slot_len = physical_slot_length(*slot_length_ptr(page, i));
+    
+      for(short j = 0; j < slot_len; j++) { 
+	assert(image[slot_offset + j] == 0xFF);
+	image[slot_offset + j] = ci;
+      }
+    }
+  }
+#endif // SLOTTED_PAGE_CHECK_FOR_OVERLAP
+#endif // SLOTTED_PAGE_SKIP_SANITY_CHECKS
+
+}
+
+
 /**
    
 Move all of the records to the beginning of the page in order to 
@@ -16,7 +130,67 @@ increase the available free space.
 The caller of this function must have a writelock on the page.
 */
 
-void slottedCompact(Page * page) {
+void slottedCompact(Page * page) { 
+  Page bufPage; 
+  byte buffer[PAGE_SIZE];
+  bufPage.memAddr = buffer;
+  
+  // Copy external headers into bufPage.
+
+  memcpy(&buffer[USABLE_SIZE_OF_PAGE], &(page->memAddr[USABLE_SIZE_OF_PAGE]), PAGE_SIZE - USABLE_SIZE_OF_PAGE);
+
+  // Now, build new slotted page in the bufPage struct.
+
+  *freespace_ptr(&bufPage) = 0;
+  // numslots_ptr will be set later.
+  *freelist_ptr(&bufPage) = INVALID_SLOT;
+
+  const short numSlots = *numslots_ptr(page);
+  short lastFreeSlot = INVALID_SLOT;
+  short lastFreeSlotBeforeUsedSlot = INVALID_SLOT;
+  short lastUsedSlot = -1;
+
+  // Rebuild free list.
+
+  for(short i = 0; i < numSlots; i++) { 
+    if(*slot_ptr(page, i) == INVALID_SLOT) { 
+      if(lastFreeSlot == INVALID_SLOT) { 
+	*freelist_ptr(&bufPage) = i;
+      } else { 
+	*slot_length_ptr(&bufPage, lastFreeSlot) = i;
+      }
+      *slot_ptr(&bufPage, i) = INVALID_SLOT;
+      lastFreeSlot = i;
+    } else {
+      lastUsedSlot = i; 
+      lastFreeSlotBeforeUsedSlot = lastFreeSlot;
+
+      short logicalSize = *slot_length_ptr(page, i);
+      short physicalSize = physical_slot_length(logicalSize);
+
+      memcpy(&(buffer[*freespace_ptr(&bufPage)]), record_ptr(page, i), physicalSize);
+
+      *slot_ptr(&bufPage, i) = *freespace_ptr(&bufPage);
+      *slot_length_ptr(&bufPage, i) = logicalSize;
+
+      (*freespace_ptr(&bufPage)) += physicalSize;
+
+    }
+  }
+  
+  // Truncate linked list, and update numslots_ptr.
+  *slot_length_ptr(&bufPage, lastFreeSlotBeforeUsedSlot) = INVALID_SLOT;
+  *numslots_ptr(&bufPage) = lastUsedSlot+1;
+  
+  memcpy(page->memAddr, buffer, PAGE_SIZE);
+
+  fsckSlottedPage(page);
+
+}
+
+void slottedCompactOld(Page * page) {
+
+  fsckSlottedPage(page);
 
 	short i;
 	Page bufPage;
@@ -50,9 +224,6 @@ void slottedCompact(Page * page) {
 	for(i = numSlots-1; i >= 0; i--) { 
 
 	  if (isValidSlot(page, i)) {
-	    /*	    printf("copying %d\n", i); 
-		    fflush(NULL); */
-	    /*  		  DEBUG("Buffer offset: %d\n", freeSpace); */
 	    recordid rid;
 
 	    rid.page = -1;
@@ -93,7 +264,7 @@ void slottedCompact(Page * page) {
 
 	memcpy(page->memAddr, buffer, PAGE_SIZE);
 	
-	assert(slottedFreespaceForSlot(page, -1) || 1);
+  fsckSlottedPage(page);
 
 }
 
@@ -119,6 +290,9 @@ void slottedCompact(Page * page) {
 // static uint64_t lastFreepage = -10; 
 
 void slottedPageInit() {
+#ifdef SLOTTED_PAGE_CHECK_FOR_OVERLAP
+  printf("slotted.c: Using expensive page sanity checking.\n");
+#endif  
   /*pthread_mutex_init(&lastFreepage_mutex , NULL);  */
   //lastFreepage = UINT64_MAX;
 }
@@ -136,6 +310,7 @@ void slottedPageInitialize(Page * page) {
   *freespace_ptr(page) = 0;
   *numslots_ptr(page)  = 0;
   *freelist_ptr(page)  = INVALID_SLOT;
+  fsckSlottedPage(page);
 
 }
 size_t slottedFreespaceUnlocked(Page * page);
@@ -191,36 +366,37 @@ size_t slottedFreespace(Page * page) {
 
 
 recordid slottedRawRalloc(Page * page, int size) {
-
   int type = size;
   size = physical_slot_length(type);
   assert(type != INVALID_SLOT);
 
   writelock(page->rwlatch, 342);
-  assert(*page_type_ptr(page) == SLOTTED_PAGE || *page_type_ptr(page) == BOUNDARY_TAG_PAGE);
+  fsckSlottedPage(page);
 
   recordid rid;
   
   rid.page = page->id;
   rid.slot = *numslots_ptr(page);
   rid.size = type;  // The rid should reflect the fact that this is a special slot.
-  
+
   /* The freelist_ptr points to the first free slot number, which 
      is the head of a linked list of free slot numbers.*/
   if(*freelist_ptr(page) != INVALID_SLOT) {
-    rid.slot = *freelist_ptr(page);
-    *freelist_ptr(page) = *slot_length_ptr(page, rid.slot);
-    *slot_length_ptr(page, rid.slot) = INVALID_SLOT;
-  }  
+    rid.slot = *freelist_ptr(page);  
+    // really_do_ralloc will look this slot up in the freelist (which
+    // is O(1), since rid.slot is the head), and then remove it from
+    // the list.
+  }
   
   really_do_ralloc(page, rid);
 
+  assert(*numslots_ptr(page) > rid.slot);
   assert(type == *slot_length_ptr(page, rid.slot));
   assert(size == physical_slot_length(*slot_length_ptr(page, rid.slot)));
 
   /*	DEBUG("slot: %d freespace: %d\n", rid.slot, freeSpace); */
   
-  assert(slottedFreespaceUnlocked(page) >= 0);
+  fsckSlottedPage(page);
 
   writeunlock(page->rwlatch);
 
@@ -268,6 +444,7 @@ static void really_do_ralloc(Page * page, recordid rid) {
     }
     while(next != INVALID_SLOT && next != rid.slot) { 
       last = next;
+      assert(next < *numslots_ptr(page));
       short next_slot_ptr = *slot_ptr(page, next);
       assert(next_slot_ptr == INVALID_SLOT);
       next = *slot_length_ptr(page, next);
@@ -324,6 +501,7 @@ static void really_do_ralloc(Page * page, recordid rid) {
     }
 
     // Terminate the end of the list.
+    assert(lastSlot < *numslots_ptr(page));
     *slot_length_ptr(page, lastSlot) = INVALID_SLOT;
 
   }
@@ -332,19 +510,19 @@ static void really_do_ralloc(Page * page, recordid rid) {
     *numslots_ptr(page) = rid.slot+1;
   }
 
+  assert(*numslots_ptr(page) > rid.slot);
+
   DEBUG("Num slots %d\trid.slot %d\n", *numslots_ptr(page), rid.slot);
   
   // Reserve space for this record and record the space's offset in
   // the slot header.
+
+  assert(rid.slot < *numslots_ptr(page));
   *freespace_ptr(page) = freeSpace + physical_slot_length(rid.size);
   *slot_ptr(page, rid.slot)  = freeSpace;
 
-  // Remember how long this record is
-  //  if(isBlob) {
-  //*slot_length_ptr(page, rid.slot = BLOB_SLOT);
-  //} else {
   *slot_length_ptr(page, rid.slot) = rid.size; 
-  //} 
+
   assert(slottedFreespaceForSlot(page, -1) || 1);
 
 }
@@ -354,6 +532,7 @@ static void really_do_ralloc(Page * page, recordid rid) {
 recordid slottedPostRalloc(int xid, Page * page, lsn_t lsn, recordid rid) {
   
 	writelock(page->rwlatch, 376);
+
 	if(rid.size >= BLOB_THRESHOLD_SIZE) { 
 	  rid.size = BLOB_SLOT;
 	}
@@ -384,26 +563,18 @@ recordid slottedPostRalloc(int xid, Page * page, lsn_t lsn, recordid rid) {
 
 	  slottedPageInitialize(page);  
 	}
+	fsckSlottedPage(page);
 
-	// Make sure the slot is invalid.  If the slot has not been used yet, then 
-	// slot_length_ptr will still be zero, so we allow that too.
-	if((*slot_length_ptr(page, rid.slot) == 0) || (*slot_ptr(page, rid.slot) == INVALID_SLOT)) {
-
+	if(*slot_ptr(page, rid.slot) == INVALID_SLOT || rid.slot >= *numslots_ptr(page)) {
 	  really_do_ralloc(page, rid);
 	
        	} else {
 
 	  // Check to see that the slot happens to be the right size,
 	  // so we are (hopefully) just overwriting a slot with
-	  // itself, or that the slot is a blob slot.  This can happen
-	  // under normal operation, since really_do_ralloc() must
-	  // be called before and after the log entry is generated.
-	  // (See comment above...)  
-	  // @todo Check to see that the blob is the right size?
-	  
-	  /*	  assert((rid.size == *slot_length_ptr(page, rid.slot)) ||
-		 (*slot_length_ptr(page, rid.slot) >= PAGE_SIZE) ||
-		 (rid.size >= BLOB_THRESHOLD_SIZE)); */
+	  // itself.  This can happen under normal operation, since
+	  // really_do_ralloc() must be called before and after the
+	  // log entry is generated.  (See comment above...)
 
 	  assert(rid.size == *slot_length_ptr(page, rid.slot));
 
@@ -413,6 +584,7 @@ recordid slottedPostRalloc(int xid, Page * page, lsn_t lsn, recordid rid) {
 
 	assert(slottedFreespaceForSlot(page, -1) || 1);
 
+        fsckSlottedPage(page);
 	writeunlock(page->rwlatch);
 
 
@@ -421,23 +593,30 @@ recordid slottedPostRalloc(int xid, Page * page, lsn_t lsn, recordid rid) {
 
 void slottedDeRalloc(int xid, Page * page, lsn_t lsn, recordid rid) {
   writelock(page->rwlatch, 443);
-  // readlock(page->rwlatch, 443);
-  size_t oldFreeLen = slottedFreespaceUnlocked(page);
-  *slot_ptr(page, rid.slot) =  INVALID_SLOT;
-  assert(*freelist_ptr(page) < *numslots_ptr(page));
-  *slot_length_ptr(page, rid.slot) = *freelist_ptr(page); 
-  *freelist_ptr(page) = rid.slot;  
-  /*  *slot_length_ptr(page, rid.slot) = 0; */
-  
+  fsckSlottedPage(page);
+
+  if(*freespace_ptr(page) == *slot_ptr(page, rid.slot) + physical_slot_length(rid.size)) {
+    (*freespace_ptr(page)) -= physical_slot_length(rid.size);
+  }
+
+  assert(rid.slot < *numslots_ptr(page));
+  if(rid.slot == *numslots_ptr(page)-1) { 
+    (*numslots_ptr(page))--;
+  } else { 
+    *slot_ptr(page, rid.slot) =  INVALID_SLOT;
+    *slot_length_ptr(page, rid.slot) = *freelist_ptr(page); 
+    *freelist_ptr(page) = rid.slot;  
+  }
+    
   pageWriteLSN(xid, page, lsn);
-  size_t newFreeLen = slottedFreespaceUnlocked(page);
-  assert(oldFreeLen <= newFreeLen);
+  fsckSlottedPage(page);
   unlock(page->rwlatch);
 }
 
 void slottedReadUnlocked(int xid, Page * page, recordid rid, byte *buff) {
   int slot_length;
 
+  fsckSlottedPage(page);
   assert(page->id == rid.page);
   slot_length = *slot_length_ptr(page, rid.slot); 
   assert((rid.size == slot_length)); // || (rid.size == BLOB_SLOT && slot_length == sizeof(blob_record_t))|| (slot_length >= PAGE_SIZE));
@@ -446,6 +625,7 @@ void slottedReadUnlocked(int xid, Page * page, recordid rid, byte *buff) {
     perror("memcpy");
     abort();
   }
+  fsckSlottedPage(page);
 
 }
 
@@ -460,6 +640,7 @@ void slottedRead(int xid, Page * page, recordid rid, byte *buff) {
 
   int slot_length;
   readlock(page->rwlatch, 519);
+  fsckSlottedPage(page);
 
   //  printf("Reading from rid = {%d,%d,%d (%d)}\n", rid.page, rid.slot, rid.size, physical_slot_length(rid.size));
 
@@ -481,15 +662,21 @@ void slottedRead(int xid, Page * page, recordid rid, byte *buff) {
     abort();
   }
 
+  fsckSlottedPage(page);
   unlock(page->rwlatch);
   
 }
 
 void slottedWrite(int xid, Page * page, lsn_t lsn, recordid rid, const byte *data) {
-  int slot_length;
 
   readlock(page->rwlatch, 529);  
   
+  slottedWriteUnlocked(xid, page, lsn, rid, data);
+
+  unlock(page->rwlatch); 
+
+
+  /*  fsckSlottedPage(page);
   //  printf("Writing to rid = {%d,%d,%d}\n", rid.page, rid.slot, rid.size);
 
 
@@ -504,11 +691,12 @@ void slottedWrite(int xid, Page * page, lsn_t lsn, recordid rid, const byte *dat
     abort();
   }
 
-  unlock(page->rwlatch); 
+  fsckSlottedPage(page); */
 
 }
 void slottedWriteUnlocked(int xid, Page * page, lsn_t lsn, recordid rid, const byte *data) {
   int slot_length;
+  fsckSlottedPage(page);
 
   //  assert(rid.size < PAGE_SIZE); 
   assert(page->id == rid.page);
@@ -520,4 +708,5 @@ void slottedWriteUnlocked(int xid, Page * page, lsn_t lsn, recordid rid, const b
     perror("memcpy");
     abort();
   }
+  fsckSlottedPage(page);
 }
diff --git a/src/lladd/page/slotted.h b/src/lladd/page/slotted.h
index 8c23e90..fb385c7 100644
--- a/src/lladd/page/slotted.h
+++ b/src/lladd/page/slotted.h
@@ -64,6 +64,9 @@ Slotted page layout:
 #define SLOTTED_PAGE_OVERHEAD_PER_RECORD (2 * sizeof(short))
 #define SLOTTED_PAGE_HEADER_OVERHEAD (3 * sizeof(short))
 
+//#define SLOTTED_PAGE_CHECK_FOR_OVERLAP 1
+#define SLOTTED_PAGE_SKIP_SANITY_CHECKS 1
+
 void slottedWrite(int xid, Page * page, lsn_t lsn, recordid rid, const byte *data);
 void slottedRead(int xid, Page * page, recordid rid, byte *buff);
 void slottedWriteUnlocked(int xid, Page * page, lsn_t lsn, recordid rid, const byte *data);