contiki/apps/antelope/index.c

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/*
* Copyright (c) 2010, Swedish Institute of Computer Science
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the Institute nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
/**
* \file
* This component forwards index calls using the generic index
* API to specific implementations.
* \author
* Nicolas Tsiftes <nvt@sics.se>
*/
#include "contiki.h"
#include "lib/memb.h"
#include "lib/list.h"
#define DEBUG DEBUG_NONE
#include "net/uip-debug.h"
#include "antelope.h"
#include "attribute.h"
#include "db-options.h"
#include "index.h"
#include "storage.h"
static index_api_t *index_components[] = {&index_inline,
&index_maxheap};
LIST(indices);
MEMB(index_memb, index_t, DB_INDEX_POOL_SIZE);
static process_event_t load_request_event;
PROCESS(db_indexer, "DB Indexer");
static index_api_t *
find_index_api(index_type_t index_type)
{
int i;
for(i = 0; i < sizeof(index_components) / sizeof(index_components[0]); i++) {
if(index_components[i]->type == index_type) {
return index_components[i];
}
}
return NULL;
}
void
index_init(void)
{
list_init(indices);
memb_init(&index_memb);
process_start(&db_indexer, NULL);
}
db_result_t
index_create(index_type_t index_type, relation_t *rel, attribute_t *attr)
{
tuple_id_t cardinality;
index_t *index;
index_api_t *api;
cardinality = relation_cardinality(rel);
if(cardinality == INVALID_TUPLE) {
return DB_STORAGE_ERROR;
}
api = find_index_api(index_type);
if(api == NULL) {
PRINTF("DB: No API for index type %d\n", (int)index_type);
return DB_INDEX_ERROR;
}
if(attr->index != NULL) {
/* Refuse to overwrite the old index. */
PRINTF("DB: The attribute %s is already indexed\n", attr->name);
return DB_INDEX_ERROR;
}
index = memb_alloc(&index_memb);
if(index == NULL) {
PRINTF("DB: Failed to allocate an index\n");
return DB_ALLOCATION_ERROR;
}
index->rel = rel;
index->attr = attr;
index->api = api;
index->flags = 0;
index->opaque_data = NULL;
index->descriptor_file[0] = '\0';
index->type = index_type;
if(DB_ERROR(api->create(index))) {
memb_free(&index_memb, index);
PRINTF("DB: Index-specific creation failed for attribute %s\n", attr->name);
return DB_INDEX_ERROR;
}
attr->index = index;
list_push(indices, index);
if(index->descriptor_file[0] != '\0' &&
DB_ERROR(storage_put_index(index))) {
api->destroy(index);
memb_free(&index_memb, index);
PRINTF("DB: Failed to store index data in file \"%s\"\n",
index->descriptor_file);
return DB_INDEX_ERROR;
}
if(!(api->flags & INDEX_API_INLINE) && cardinality > 0) {
PRINTF("DB: Created an index for an old relation; issuing a load request\n");
index->flags = INDEX_LOAD_NEEDED;
process_post(&db_indexer, load_request_event, NULL);
} else {
PRINTF("DB: Index created for attribute %s\n", attr->name);
index->flags |= INDEX_READY;
}
return DB_OK;
}
db_result_t
index_destroy(index_t *index)
{
if(DB_ERROR(index_release(index)) ||
DB_ERROR(index->api->destroy(index))) {
return DB_INDEX_ERROR;
}
return DB_OK;
}
db_result_t
index_load(relation_t *rel, attribute_t *attr)
{
index_t *index;
index_api_t *api;
PRINTF("DB: Attempting to load an index over %s.%s\n", rel->name, attr->name);
index = memb_alloc(&index_memb);
if(index == NULL) {
PRINTF("DB: No more index objects available\n");
return DB_ALLOCATION_ERROR;
}
if(DB_ERROR(storage_get_index(index, rel, attr))) {
PRINTF("DB: Failed load an index descriptor from storage\n");
memb_free(&index_memb, index);
return DB_INDEX_ERROR;
}
index->rel = rel;
index->attr = attr;
index->opaque_data = NULL;
api = find_index_api(index->type);
if(api == NULL) {
PRINTF("DB: No API for index type %d\n", index->type);
return DB_INDEX_ERROR;
}
index->api = api;
if(DB_ERROR(api->load(index))) {
PRINTF("DB: Index-specific load failed\n");
return DB_INDEX_ERROR;
}
list_push(indices, index);
attr->index = index;
index->flags = INDEX_READY;
return DB_OK;
}
db_result_t
index_release(index_t *index)
{
if(DB_ERROR(index->api->release(index))) {
return DB_INDEX_ERROR;
}
index->attr->index = NULL;
list_remove(indices, index);
memb_free(&index_memb, index);
return DB_OK;
}
db_result_t
index_insert(index_t *index, attribute_value_t *value,
tuple_id_t tuple_id)
{
return index->api->insert(index, value, tuple_id);
}
db_result_t
index_delete(index_t *index, attribute_value_t *value)
{
if(index->flags != INDEX_READY) {
return DB_INDEX_ERROR;
}
return index->api->delete(index, value);
}
db_result_t
index_get_iterator(index_iterator_t *iterator, index_t *index,
attribute_value_t *min_value,
attribute_value_t *max_value)
{
tuple_id_t cardinality;
unsigned long range;
unsigned long max_range;
long max;
long min;
cardinality = relation_cardinality(index->rel);
if(cardinality == INVALID_TUPLE) {
return DB_STORAGE_ERROR;
}
if(index->flags != INDEX_READY) {
return DB_INDEX_ERROR;
}
min = db_value_to_long(min_value);
max = db_value_to_long(max_value);
range = (unsigned long)max - min;
if(range > 0) {
/*
* Index structures that do not have a natural ability to handle
* range queries (e.g., a hash index) can nevertheless emulate them.
*
* The range query emulation attempts to look up the key for each
* value in the search range. If the search range is sparse, this
* iteration will incur a considerable overhead per found key.
*
* Hence, The emulation is preferable when an external module wants
* to iterate over a narrow range of keys, for which the total
* search cost is smaller than that of an iteration over all tuples
* in the relation.
*/
if(!(index->api->flags & INDEX_API_RANGE_QUERIES)) {
PRINTF("DB: Range query requested for an index that does not support it\n");
max_range = cardinality / DB_INDEX_COST;
if(range > max_range) {
return DB_INDEX_ERROR;
}
PRINTF("DB: Using the index anyway because the range is small enough (%lu <= %lu)\n",
range, max_range);
}
}
iterator->index = index;
iterator->min_value = *min_value;
iterator->max_value = *max_value;
iterator->next_item_no = 0;
PRINTF("DB: Acquired an index iterator for %s.%s over the range (%ld,%ld)\n",
index->rel->name, index->attr->name,
min_value->u.long_value, max_value->u.long_value);
return DB_OK;
}
tuple_id_t
index_get_next(index_iterator_t *iterator)
{
long min;
long max;
if(iterator->index == NULL) {
/* This attribute is not indexed. */
return INVALID_TUPLE;
}
if((iterator->index->attr->flags & ATTRIBUTE_FLAG_UNIQUE) &&
iterator->next_item_no == 1) {
min = db_value_to_long(&iterator->min_value);
max = db_value_to_long(&iterator->max_value);
if(min == max) {
/*
* We stop if this is an equivalence search on an attribute
* whose values are unique, and we already found one item.
*/
PRINTF("DB: Equivalence search finished\n");
return INVALID_TUPLE;
}
}
return iterator->index->api->get_next(iterator);
}
int
index_exists(attribute_t *attr)
{
index_t *index;
index = (index_t *)attr->index;
if(index == NULL || index->flags != INDEX_READY) {
return 0;
}
return 1;
}
static index_t *
get_next_index_to_load(void)
{
index_t *index;
for(index = list_head(indices); index != NULL; index = index->next) {
if(index->flags & INDEX_LOAD_NEEDED) {
return index;
}
}
return NULL;
}
PROCESS_THREAD(db_indexer, ev, data)
{
static index_t *index;
static db_handle_t handle;
static tuple_id_t row;
db_result_t result;
attribute_value_t value;
int column;
PROCESS_BEGIN();
load_request_event = process_alloc_event();
for(;;) {
PROCESS_WAIT_EVENT_UNTIL(ev == load_request_event);
index = get_next_index_to_load();
if(index == NULL) {
PRINTF("DB: Request to load an index, but no index is set to be loaded\n");
continue;
}
PRINTF("DB: Loading the index for %s.%s...\n",
index->rel->name, index->attr->name);
if(DB_ERROR(db_query(&handle, "SELECT %s FROM %s;", index->attr->name, index->rel->name))) {
index->flags |= INDEX_LOAD_ERROR;
index->flags &= ~INDEX_LOAD_NEEDED;
continue;
}
for(;; row++) {
PROCESS_PAUSE();
result = db_process(&handle);
if(DB_ERROR(result)) {
PRINTF("DB: Index loading failed while processing: %s\n",
db_get_result_message(result));
index->flags |= INDEX_LOAD_ERROR;
goto cleanup;
}
if(result == DB_FINISHED) {
break;
}
for(column = 0; column < handle.ncolumns; column++) {
if(DB_ERROR(db_get_value(&value, &handle, column))) {
index->flags |= INDEX_LOAD_ERROR;
goto cleanup;
}
if(DB_ERROR(index_insert(index, &value, row))) {
index->flags |= INDEX_LOAD_ERROR;
goto cleanup;
}
}
}
PRINTF("DB: Loaded %lu rows into the index\n",
(unsigned long)handle.current_row);
cleanup:
if(index->flags & INDEX_LOAD_ERROR) {
PRINTF("DB: Failed to load the index for %s.%s\n",
index->rel->name, index->attr->name);
}
index->flags &= ~INDEX_LOAD_NEEDED;
index->flags |= INDEX_READY;
db_free(&handle);
}
PROCESS_END();
}