/* Copyright (c) 2009, 2010 Nicira, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at:
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <config.h>

#include "query.h"

#include "column.h"
#include "condition.h"
#include "row.h"
#include "table.h"

void
ovsdb_query(struct ovsdb_table *table, const struct ovsdb_condition *cnd,
            bool (*output_row)(const struct ovsdb_row *, void *aux), void *aux)
{
    if (cnd->n_clauses > 0
        && cnd->clauses[0].column->index == OVSDB_COL_UUID
        && cnd->clauses[0].function == OVSDB_F_EQ) {
        /* Optimize the case where the query has a clause of the form "uuid ==
         * <some-uuid>", since we have an index on UUID. */
        const struct ovsdb_row *row;

        row = ovsdb_table_get_row(table, &cnd->clauses[0].arg.keys[0].uuid);
        if (row && row->table == table && ovsdb_condition_evaluate(row, cnd)) {
            output_row(row, aux);
        }
    } else {
        /* Linear scan. */
        const struct ovsdb_row *row, *next;

        HMAP_FOR_EACH_SAFE (row, next, hmap_node, &table->rows) {
            if (ovsdb_condition_evaluate(row, cnd) && !output_row(row, aux)) {
                break;
            }
        }
    }
}

static bool
query_row_set_cb(const struct ovsdb_row *row, void *results_)
{
    struct ovsdb_row_set *results = results_;
    ovsdb_row_set_add_row(results, row);
    return true;
}

void
ovsdb_query_row_set(struct ovsdb_table *table,
                    const struct ovsdb_condition *condition,
                    struct ovsdb_row_set *results)
{
    ovsdb_query(table, condition, query_row_set_cb, results);
}

static bool
query_distinct_cb(const struct ovsdb_row *row, void *hash_)
{
    struct ovsdb_row_hash *hash = hash_;
    ovsdb_row_hash_insert(hash, row);
    return true;
}

void
ovsdb_query_distinct(struct ovsdb_table *table,
                     const struct ovsdb_condition *condition,
                     const struct ovsdb_column_set *columns,
                     struct ovsdb_row_set *results)
{
    if (!columns || ovsdb_column_set_contains(columns, OVSDB_COL_UUID)) {
        /* All the result rows are guaranteed to be distinct anyway. */
        return ovsdb_query_row_set(table, condition, results);
    } else {
        /* Use hash table to drop duplicates. */
        struct ovsdb_row_hash_node *node;
        struct ovsdb_row_hash hash;

        ovsdb_row_hash_init(&hash, columns);
        ovsdb_query(table, condition, query_distinct_cb, &hash);
        HMAP_FOR_EACH (node, hmap_node, &hash.rows) {
            ovsdb_row_set_add_row(results, node->row);
        }
        ovsdb_row_hash_destroy(&hash, false);
    }
}
