Version 2.4.1
ex_schema.c

Shows how to create column-oriented data and access individual columns.

/*-
* 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_schema.c
* This is an example application demonstrating how to create and access
* tables using a schema.
*/
#include <inttypes.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <wiredtiger.h>
static const char *home;
/* The C struct for the data we are storing in a WiredTiger table. */
typedef struct {
char country[5];
uint16_t year;
uint64_t population;
} POP_RECORD;
static POP_RECORD pop_data[] = {
{ "AU", 1900, 4000000 },
{ "AU", 2000, 19053186 },
{ "CAN", 1900, 5500000 },
{ "CAN", 2000, 31099561 },
{ "UK", 1900, 369000000 },
{ "UK", 2000, 59522468 },
{ "USA", 1900, 76212168 },
{ "USA", 2000, 301279593 },
{ "", 0, 0 }
};
int
main(void)
{
POP_RECORD *p;
WT_CONNECTION *conn;
WT_CURSOR *cursor;
WT_SESSION *session;
const char *country;
uint64_t recno, population;
uint16_t year;
int ret;
/*
* 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 (ret);
}
/* Note: error checking omitted for clarity. */
ret = conn->open_session(conn, NULL, NULL, &session);
/*
* Create the population table.
* Keys are record numbers, the format for values is (5-byte string,
* uint16_t, uint64_t).
* See ::wiredtiger_struct_pack for details of the format strings.
*/
ret = session->create(session, "table:poptable",
"key_format=r,"
"value_format=5sHQ,"
"columns=(id,country,year,population),"
"colgroups=(main,population)");
/*
* Create two column groups: a primary column group with the country
* code, year and population (named "main"), and a population column
* group with the population by itself (named "population").
*/
ret = session->create(session,
"colgroup:poptable:main", "columns=(country,year,population)");
ret = session->create(session,
"colgroup:poptable:population", "columns=(population)");
/* Create an index with a simple key. */
ret = session->create(session,
"index:poptable:country", "columns=(country)");
/* Create an index with a composite key (country,year). */
ret = session->create(session,
"index:poptable:country_plus_year", "columns=(country,year)");
/* Insert the records into the table. */
ret = session->open_cursor(
session, "table:poptable", NULL, "append", &cursor);
for (p = pop_data; p->year != 0; p++) {
cursor->set_value(cursor, p->country, p->year, p->population);
ret = cursor->insert(cursor);
}
ret = cursor->close(cursor);
/* List the records in the table. */
ret = session->open_cursor(session,
"table:poptable", NULL, NULL, &cursor);
while ((ret = cursor->next(cursor)) == 0) {
ret = cursor->get_key(cursor, &recno);
ret = cursor->get_value(cursor, &country, &year, &population);
printf("ID %" PRIu64, recno);
printf(": country %s, year %u, population %" PRIu64 "\n",
country, year, population);
}
ret = cursor->close(cursor);
/* List the records in the table using raw mode. */
ret = session->open_cursor(session,
"table:poptable", NULL, "raw", &cursor);
while ((ret = cursor->next(cursor)) == 0) {
WT_ITEM key, value;
ret = cursor->get_key(cursor, &key);
ret = wiredtiger_struct_unpack(session,
key.data, key.size, "r", &recno);
printf("ID %" PRIu64, recno);
ret = cursor->get_value(cursor, &value);
ret = wiredtiger_struct_unpack(session,
value.data, value.size,
"5sHQ", &country, &year, &population);
printf(": country %s, year %u, population %" PRIu64 "\n",
country, year, population);
}
ret = cursor->close(cursor);
/*
* Open a cursor on the main column group, and return the information
* for a particular country.
*/
ret = session->open_cursor(
session, "colgroup:poptable:main", NULL, NULL, &cursor);
cursor->set_key(cursor, 2);
if ((ret = cursor->search(cursor)) == 0) {
ret = cursor->get_value(cursor, &country, &year, &population);
printf("ID 2: country %s, year %u, population %" PRIu64 "\n",
country, year, population);
}
ret = cursor->close(cursor);
/*
* Open a cursor on the population column group, and return the
* population of a particular country.
*/
ret = session->open_cursor(session,
"colgroup:poptable:population", NULL, NULL, &cursor);
cursor->set_key(cursor, 2);
if ((ret = cursor->search(cursor)) == 0) {
ret = cursor->get_value(cursor, &population);
printf("ID 2: population %" PRIu64 "\n", population);
}
ret = cursor->close(cursor);
/* Search in a simple index. */
ret = session->open_cursor(session,
"index:poptable:country", NULL, NULL, &cursor);
cursor->set_key(cursor, "AU\0\0\0");
ret = cursor->search(cursor);
ret = cursor->get_value(cursor, &country, &year, &population);
printf("AU: country %s, year %u, population %" PRIu64 "\n",
country, (unsigned int)year, population);
ret = cursor->close(cursor);
/* Search in a composite index. */
ret = session->open_cursor(session,
"index:poptable:country_plus_year", NULL, NULL, &cursor);
cursor->set_key(cursor, "USA\0\0", (uint16_t)1900);
ret = cursor->search(cursor);
ret = cursor->get_value(cursor, &country, &year, &population);
printf("US 1900: country %s, year %u, population %" PRIu64 "\n",
country, (unsigned int)year, population);
ret = cursor->close(cursor);
/*
* Use a projection to return just the table's country and year
* columns.
*/
ret = session->open_cursor(session,
"table:poptable(country,year)", NULL, NULL, &cursor);
while ((ret = cursor->next(cursor)) == 0) {
ret = cursor->get_value(cursor, &country, &year);
printf("country %s, year %u\n", country, year);
}
ret = cursor->close(cursor);
/*
* Use a projection to return just the table's country and year
* columns, using raw mode.
*/
ret = session->open_cursor(session,
"table:poptable(country,year)", NULL, "raw", &cursor);
while ((ret = cursor->next(cursor)) == 0) {
WT_ITEM value;
ret = cursor->get_value(cursor, &value);
ret = wiredtiger_struct_unpack(
session, value.data, value.size, "5sH", &country, &year);
printf("country %s, year %u\n", country, year);
}
ret = cursor->close(cursor);
/*
* Use a projection to return just the table's record number key
* from an index.
*/
ret = session->open_cursor(session,
"index:poptable:country_plus_year(id)", NULL, NULL, &cursor);
while ((ret = cursor->next(cursor)) == 0) {
ret = cursor->get_key(cursor, &country, &year);
ret = cursor->get_value(cursor, &recno);
printf("row ID %" PRIu64 ": country %s, year %u\n",
recno, country, year);
}
ret = cursor->close(cursor);
/*
* Use a projection to return just the population column from an
* index.
*/
ret = session->open_cursor(session,
"index:poptable:country_plus_year(population)",
NULL, NULL, &cursor);
while ((ret = cursor->next(cursor)) == 0) {
ret = cursor->get_key(cursor, &country, &year);
ret = cursor->get_value(cursor, &population);
printf("population %" PRIu64 ": country %s, year %u\n",
population, country, year);
}
ret = cursor->close(cursor);
/*
* Use a projection to avoid accessing any other column groups when
* using an index: supply an empty list of value columns.
*/
ret = session->open_cursor(session,
"index:poptable:country_plus_year()", NULL, NULL, &cursor);
while ((ret = cursor->next(cursor)) == 0) {
ret = cursor->get_key(cursor, &country, &year);
printf("country %s, year %u\n", country, year);
}
ret = cursor->close(cursor);
ret = conn->close(conn, NULL);
return (ret);
}