A more complex schema based on a call center example, showing how to map some SQL constructs onto the WiredTiger API.
/*- * Copyright (c) 2008-2012 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 <string.h> #include <wiredtiger.h> const char *home = "WT_TEST"; /* * 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; char *name; char *address; char *phone; } CUSTOMER; /* Call records. */ typedef struct { uint64_t id; uint64_t call_date; uint64_t cust_id; uint64_t emp_id; char *call_type; char *notes; } CALL; int main(void) { int count, exact, ret; WT_CONNECTION *conn; WT_SESSION *session; WT_CURSOR *cursor; CUSTOMER cust; CALL call; ret = wiredtiger_open(home, NULL, "create", &conn); if (ret != 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=S," "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)"); /* * Create the calls table, give names and types to the columns. * All of 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 customers table with some data. */ ret = session->open_cursor( session, "table:customers", NULL, NULL, &cursor); cursor->set_key(cursor, "customer #1"); cursor->set_value(cursor, "Professor Oak", "LeafGreen Avenue", "123-456-7890"); ret = cursor->insert(cursor); cursor->set_key(cursor, "customer #2"); cursor->set_value(cursor, "Lorelei", "Sevii Islands", "098-765-4321"); 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, "212-555-1000"); ret = cursor->search(cursor); if (ret == 0) { ret = cursor->get_value(cursor, &cust.id, &cust.name); printf("Got customer record for %s\n", cust.name); } 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. If these were all * covered by the index, the primary would not 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. */ 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. * Otherwise the cursor will on a matching key if one exists, or on an * adjacent key. If the key we find is equal or larger than the search * key, go back one. */ if (ret == 0 && exact >= 0) ret = cursor->prev(cursor); if (ret == 0) ret = cursor->get_value(cursor, &call.cust_id, &call.call_type, &call.notes); count = 0; while (ret == 0 && call.cust_id == cust.id) { printf("Got call record on date %lu: type %s: %s\n", (unsigned long)call.call_date, call.call_type, call.notes); if (++count == 3) break; ret = cursor->prev(cursor); ret = cursor->get_value(cursor, &call.cust_id, &call.call_type, &call.notes); } ret = conn->close(conn, NULL); return (ret); }