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