ex_call_center.c

A more complex schema based on a call center example, showing how to map some SQL constructs onto the WiredTiger API.

/*-
 * Public Domain 2008-2014 WiredTiger, Inc.
 *
 * This is free and unencumbered software released into the public domain.
 *
 * Anyone is free to copy, modify, publish, use, compile, sell, or
 * distribute this software, either in source code form or as a compiled
 * binary, for any purpose, commercial or non-commercial, and by any
 * means.
 *
 * In jurisdictions that recognize copyright laws, the author or authors
 * of this software dedicate any and all copyright interest in the
 * software to the public domain. We make this dedication for the benefit
 * of the public at large and to the detriment of our heirs and
 * successors. We intend this dedication to be an overt act of
 * relinquishment in perpetuity of all present and future rights to this
 * software under copyright law.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 *
 * ex_call_center.c
 *      This is an example application that demonstrates how to map a
 *      moderately complex SQL application into WiredTiger.
 */

#include <inttypes.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <wiredtiger.h>

static const char *home;

/*
 * In SQL, the tables are described as follows:
 *
 * CREATE TABLE Customers(id INTEGER PRIMARY KEY,
 *     name VARCHAR(30), address VARCHAR(50), phone VARCHAR(15))
 * CREATE INDEX CustomersPhone ON Customers(phone)
 *
 * CREATE TABLE Calls(id INTEGER PRIMARY KEY, call_date DATE,
 *     cust_id INTEGER, emp_id INTEGER, call_type VARCHAR(12),
 *     notes VARCHAR(25))
 * CREATE INDEX CallsCustDate ON Calls(cust_id, call_date)
 *
 * In this example, both tables will use record numbers for their IDs, which
 * will be the key.  The C structs for the records are as follows.
 */

/* Customer records. */
typedef struct {
        uint64_t id;
        const char *name;
        const char *address;
        const char *phone;
} CUSTOMER;

/* Call records. */
typedef struct {
        uint64_t id;
        uint64_t call_date;
        uint64_t cust_id;
        uint64_t emp_id;
        const char *call_type;
        const char *notes;
} CALL;
int
main(void)
{
        int count, exact, ret;
        WT_CONNECTION *conn;
        WT_SESSION *session;
        WT_CURSOR *cursor;
        CUSTOMER cust, *custp, cust_sample[] = {
                { 0, "Professor Oak", "LeafGreen Avenue", "123-456-7890" },
                { 0, "Lorelei", "Sevii Islands", "098-765-4321" },
                { 0, NULL, NULL, NULL }
        };
        CALL call, *callp, call_sample[] = {
                { 0, 32, 1, 2, "billing", "unavailable" },
                { 0, 33, 1, 2, "billing", "available" },
                { 0, 34, 1, 2, "reminder", "unavailable" },
                { 0, 35, 1, 2, "reminder", "available" },
                { 0, 0, 0, 0, NULL, NULL }
        };

        /*
         * Create a clean test directory for this run of the test program if the
         * environment variable isn't already set (as is done by make check).
         */
        if (getenv("WIREDTIGER_HOME") == NULL) {
                home = "WT_HOME";
                ret = system("rm -rf WT_HOME && mkdir WT_HOME");
        } else
                home = NULL;

        if ((ret = wiredtiger_open(home, NULL, "create", &conn)) != 0) {
                fprintf(stderr, "Error connecting to %s: %s\n",
                    home, wiredtiger_strerror(ret));
                return (1);
        }
        /* Note: further error checking omitted for clarity. */

        ret = conn->open_session(conn, NULL, NULL, &session);

        /*
         * Create the customers table, give names and types to the columns.
         * The columns will be stored in two groups: "main" and "address",
         * created below.
         */
        ret = session->create(session, "table:customers",
            "key_format=r,"
            "value_format=SSS,"
            "columns=(id,name,address,phone),"
            "colgroups=(main,address)");

        /* Create the main column group with value columns except address. */
        ret = session->create(session,
            "colgroup:customers:main", "columns=(name,phone)");

        /* Create the address column group with just the address. */
        ret = session->create(session,
            "colgroup:customers:address", "columns=(address)");

        /* Create an index on the customer table by phone number. */
        ret = session->create(session,
            "index:customers:phone", "columns=(phone)");

        /* Populate the customers table with some data. */
        ret = session->open_cursor(
            session, "table:customers", NULL, "append", &cursor);
        for (custp = cust_sample; custp->name != NULL; custp++) {
                cursor->set_value(cursor,
                    custp->name, custp->address, custp->phone);
                ret = cursor->insert(cursor);
        }
        ret = cursor->close(cursor);

        /*
         * Create the calls table, give names and types to the columns.  All the
         * columns will be stored together, so no column groups are declared.
         */
        ret = session->create(session, "table:calls",
            "key_format=r,"
            "value_format=qrrSS,"
            "columns=(id,call_date,cust_id,emp_id,call_type,notes)");

        /*
         * Create an index on the calls table with a composite key of cust_id
         * and call_date.
         */
        ret = session->create(session, "index:calls:cust_date",
            "columns=(cust_id,call_date)");

        /* Populate the calls table with some data. */
        ret = session->open_cursor(
            session, "table:calls", NULL, "append", &cursor);
        for (callp = call_sample; callp->call_type != NULL; callp++) {
                cursor->set_value(cursor, callp->call_date, callp->cust_id,
                    callp->emp_id, callp->call_type, callp->notes);
                ret = cursor->insert(cursor);
        }
        ret = cursor->close(cursor);

        /*
         * First query: a call arrives.  In SQL:
         *
         * SELECT id, name FROM Customers WHERE phone=?
         *
         * Use the cust_phone index, lookup by phone number to fill the
         * customer record.  The cursor will have a key format of "S" for a
         * string because the cust_phone index has a single column ("phone"),
         * which is of type "S".
         *
         * Specify the columns we want: the customer ID and the name.  This
         * means the cursor's value format will be "rS".
         */
        ret = session->open_cursor(session,
            "index:customers:phone(id,name)", NULL, NULL, &cursor);
        cursor->set_key(cursor, "123-456-7890");
        ret = cursor->search(cursor);
        if (ret == 0) {
                ret = cursor->get_value(cursor, &cust.id, &cust.name);
                printf("Read customer record for %s (ID %" PRIu64 ")\n",
                    cust.name, cust.id);
        }
        ret = cursor->close(cursor);

        /*
         * Next query: get the recent order history.  In SQL:
         *
         * SELECT * FROM Calls WHERE cust_id=? ORDER BY call_date DESC LIMIT 3
         *
         * Use the call_cust_date index to find the matching calls.  Since it is
         * is in increasing order by date for a given customer, we want to start
         * with the last record for the customer and work backwards.
         *
         * Specify a subset of columns to be returned.  (Note that if these were
         * all covered by the index, the primary would not have to be accessed.)
         * Stop after getting 3 records.
         */
        ret = session->open_cursor(session,
            "index:calls:cust_date(cust_id,call_type,notes)",
            NULL, NULL, &cursor);

        /*
         * The keys in the index are (cust_id,call_date) -- we want the largest
         * call date for a given cust_id.  Search for (cust_id+1,0), then work
         * backwards.
         */
        cust.id = 1;
        cursor->set_key(cursor, cust.id + 1, 0);
        ret = cursor->search_near(cursor, &exact);

        /*
         * If the table is empty, search_near will return WT_NOTFOUND, else the
         * cursor will be positioned on a matching key if one exists, or an
         * adjacent key if one does not.  If the positioned key is equal to or
         * larger than the search key, go back one.
         */
        if (ret == 0 && exact >= 0)
                ret = cursor->prev(cursor);
        for (count = 0; ret == 0 && count < 3; ++count) {
                ret = cursor->get_value(cursor,
                    &call.cust_id, &call.call_type, &call.notes);
                if (call.cust_id != cust.id)
                        break;
                printf("Call record: customer %" PRIu64 " (%s: %s)\n",
                    call.cust_id, call.call_type, call.notes);
                ret = cursor->prev(cursor);
        }
        ret = conn->close(conn, NULL);

        return (ret);
}