feat(lsm): pave the way for removals and updates

lsm/include/lsm/store.h

@@ -7,8 +7,6 @@
 #include "lsm.h"
 #include "lsm/str.h"
 
-#define LSM_STORE_DISK_THRESHOLD 1024
-
 /**
  * A handle referencing an entry inside a store. Read/write operations from/to
  * the entry go through this handle.

lsm/src/_include/lsm/store_internal.h

@@ -19,9 +19,8 @@ typedef struct lsm_attr {
 /**
  * An entry inside an LSM store.
  *
- * Each entry consists of the key it's stored behind, zero  or more attributes
- * (metadata) and a data field. The data field can be stored on disk or
- * in-memory, depending on the size.
+ * Each entry consists of the key it's stored behind, zero or more attributes
+ * (metadata) and a data file.
  */
 typedef struct lsm_entry {
   lsm_str *key;
@@ -56,6 +55,12 @@ typedef struct lsm_entry_wrapper {
 lsm_error lsm_entry_wrapper_init(lsm_entry_wrapper **ptr);
 void lsm_entry_wrapper_free(lsm_entry_wrapper *wrapper);
 
+typedef enum lsm_entry_handle_state : uint8_t {
+  lsm_entry_handle_state_new = 1 << 0,
+  lsm_entry_handle_state_updated = 1 << 1,
+  lsm_entry_handle_state_removed = 1 << 2,
+} lsm_entry_handle_state;
+
 struct lsm_entry_handle {
   lsm_entry_wrapper *wrapper;
   lsm_store *store;
@@ -63,8 +68,8 @@ struct lsm_entry_handle {
   FILE *f;
   // Current position in the file pointer
   uint64_t pos;
-  // Whether the entry's metadata has changed
-  bool dirty;
+  // Required to determine in what way the database files need to be synced
+  uint64_t states;
 };
 
 lsm_error lsm_entry_handle_init(lsm_entry_handle **out);
@@ -100,10 +105,17 @@ lsm_error lsm_store_load_db(lsm_store *store);
 lsm_error lsm_entry_disk_insert(lsm_entry_handle *handle);
 
 /**
- * Remove an entry from the database
+ * Remove an entry from the database.
  *
  * @param handle handle to the removed entry
  */
 lsm_error lsm_entry_disk_remove(lsm_entry_handle *handle);
 
+/**
+ * Update an existing entry already in the store.
+ *
+ * @param handle to updated entry
+ */
+lsm_error lsm_entry_disk_update(lsm_entry_handle *handle);
+
 #endif

lsm/src/store/lsm_store.c

@@ -151,7 +151,7 @@ lsm_error lsm_store_insert(lsm_entry_handle **out, lsm_store *store,
   handle->store = store;
 
   // Newly inserted entries are always dirty
-  handle->dirty = true;
+  handle->states |= lsm_entry_handle_state_new;
 
   *out = handle;
 
@@ -192,7 +192,7 @@ lsm_error lsm_entry_data_append(lsm_entry_handle *handle, lsm_str *data) {
   }
 
   entry->data_len = new_len;
-  handle->dirty = true;
+  handle->states |= lsm_entry_handle_state_updated;
 
   return lsm_error_ok;
 }

lsm/src/store/lsm_store_disk_read.c

@@ -173,9 +173,7 @@ lsm_error lsm_store_load_db(lsm_store *store) {
 
       handle->wrapper->entry->idx_file_offset = idx_file_offset;
 
-      // We explicitely set the dirty flag here to prevent writing to the datase
-      // when reading it in
-      handle->dirty = false;
+      handle->states = 0;
       lsm_entry_close(handle);
 
       store->db_file_size += db_dim[1];

lsm/src/store/lsm_store_entry.c

@@ -53,8 +53,14 @@ void lsm_entry_close(lsm_entry_handle *handle) {
   }
 
   // TODO handle errors here
-  if (handle->dirty) {
+  if ((handle->states & lsm_entry_handle_state_new) &&
+      !(handle->states & lsm_entry_handle_state_removed)) {
     lsm_entry_disk_insert(handle);
+  } else if ((handle->states & lsm_entry_handle_state_removed) &&
+             !(handle->states & lsm_entry_handle_state_new)) {
+    /* lsm_entry_disk_remove(handle); */
+  } else if (handle->states & lsm_entry_handle_state_updated) {
+    /* lsm_entry_disk_update(handle); */
   }
 
   pthread_rwlock_unlock(&handle->wrapper->lock);
@@ -157,7 +163,7 @@ lsm_error lsm_entry_attr_remove(lsm_str **out, lsm_entry_handle *handle,
   entry->attrs.count--;
   entry->attrs.bitmap[type / 64] &= ~(((uint64_t)1) << (type % 64));
 
-  handle->dirty = true;
+  handle->states |= lsm_entry_handle_state_updated;
 
   return lsm_error_ok;
 }
@@ -184,7 +190,7 @@ lsm_error lsm_entry_attr_insert(lsm_entry_handle *handle, uint8_t type,
   entry->attrs.count++;
   entry->attrs.bitmap[type / 64] |= ((uint64_t)1) << (type % 64);
 
-  handle->dirty = true;
+  handle->states |= lsm_entry_handle_state_updated;
 
   return lsm_error_ok;
 }