SpatialLite使用

说实话，这是第一次使用到空间数据库SpatialLite，在前几天解决了一个困扰了我好久的问题，就是如何在查询空间数据库中和某一经纬度最近的数据库中有的经纬度的水深点，最后通过一个偏移变量来解决了，具体sql去下。

destLon -= 0.001* 2^n  <= destLon <=  destLon +=  0.001* 2^n
destLat -= 0.001* 2^n  <= destLat <=  destLat +=  0.001* 2^n

select astext(geom),depth from layer_mapnikds_soundg where X(geom) >110.822859 AND X(geom)<110.824859 AND Y(geom) > 19.502397 AND Y(geom)< 19.504397

这样过后，然后就需要在c++中来实现操作SpatialLite数据库了。

那么如何去连接SpatialLite呢？首先就是要配置SpatialLite的环境，包括他的库引入什么的就不多做介绍了，下面来看看SpatialLite的具体执行流程把。

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

//包含spatialite库
#ifdef SPATIALITE_AMALGAMATION
#include <spatialite/sqlite3.h>
#else
#include <sqlite3.h>
#endif

#ifndef SPATIALITE_EXTENSION
#include <spatialite.h>
#endif

int main(void)
{
sqlite3 *db_handle;
sqlite3_stmt *stmt;
int ret;
char *err_msg = NULL;
char sql[2048];
char sql2[1024];
int i;
char **results;
int rows;
int columns;
int cnt;
const char *type;
int srid;
char name[1024];
char geom[2048];

#ifndef SPATIALITE_EXTENSION
/*
* initializing SpatiaLite-Amalgamation
*
* any C/C++ source requires this to be performed
* for each connection before invoking the first
* SQLite/SpatiaLite call
*/
spatialite_init(0);
fprintf(stderr, "\n\n******* hard-linked libspatialite ********\n\n");
#endif

/* creating/connecting the test_db */
//测试和连接 test_db
ret = sqlite3_open_v2("test-db.sqlite", &db_handle,
SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE, NULL);
if (ret != SQLITE_OK)
{
fprintf(stderr, "cannot open 'test-db.sqlite': %s\n",
sqlite3_errmsg(db_handle));
sqlite3_close(db_handle);
db_handle = NULL;
return -1;
}

#ifdef SPATIALITE_EXTENSION
/*
* loading SpatiaLite as an extension
//加载  SpatiaLite 扩展
*/
sqlite3_enable_load_extension(db_handle, 1);
strcpy(sql, "SELECT load_extension('libspatialite.so')");
ret = sqlite3_exec(db_handle, sql, NULL, NULL, &err_msg);
if (ret != SQLITE_OK)
{
fprintf(stderr, "load_extension() error: %s\n", err_msg);
sqlite3_free(err_msg);
return 0;
}
fprintf(stderr, "\n\n**** SpatiaLite loaded as an extension ***\n\n");
#endif

/* reporting version infos */
#ifndef SPATIALITE_EXTENSION
/*
* please note well:
* this process is physically linked to libspatialite
* so we can directly call any SpatiaLite's API function
//打印版本信息，确保能够正确的使用库函数
*/
fprintf(stderr, "SQLite version: %s\n", sqlite3_libversion());
fprintf(stderr, "SpatiaLite version: %s\n", spatialite_version());
#else
/*
* please note well:
* this process isn't physically linked to libspatialite
* because we loaded the library as an extension
//注意：我们链接的不是一个物理的spatialite库，所以要将这个库以扩展的形势加载

*
* so we aren't enabled to directly call any SpatiaLite's API functions
* we simply can access SpatiaLite indirectly via SQL statements
//我们不能直接访问spatialLite API函数，但是我们可以通过sql间接访问spatialLite

*/
strcpy(sql, "SELECT sqlite_version()");
ret =
sqlite3_get_table(db_handle, sql, &results, &rows, &columns, &err_msg);
if (ret != SQLITE_OK)
{
fprintf(stderr, "Error: %s\n", err_msg);
sqlite3_free(err_msg);
goto stop;
}
if (rows < 1)
{
fprintf(stderr,
"Unexpected error: sqlite_version() not found ??????\n");
goto stop;
}
else
{
for (i = 1; i <= rows; i++)
{
fprintf(stderr, "SQLite version: %s\n",
results[(i * columns) + 0]);
}
}
sqlite3_free_table(results);
strcpy(sql, "SELECT spatialite_version()");
ret =
sqlite3_get_table(db_handle, sql, &results, &rows, &columns, &err_msg);
if (ret != SQLITE_OK)
{
fprintf(stderr, "Error: %s\n", err_msg);
sqlite3_free(err_msg);
goto stop;
}
if (rows < 1)
{
fprintf(stderr,
"Unexpected error: spatialite_version() not found ??????\n");
goto stop;
}
else
{
for (i = 1; i <= rows; i++)
{
fprintf(stderr, "SpatiaLite version: %s\n",
results[(i * columns) + 0]);
}
}
sqlite3_free_table(results);
#endif /* SpatiaLite as an extension */

/* initializing SpatiaLite's metadata tables */、
//初始化spatialLite元数据表
strcpy(sql, "SELECT InitSpatialMetadata()");
ret = sqlite3_exec(db_handle, sql, NULL, NULL, &err_msg);
if (ret != SQLITE_OK)
{
fprintf(stderr, "InitSpatialMetadata() error: %s\n", err_msg);
sqlite3_free(err_msg);
return 0;
}

/* creating a POINT table */
//创建一个POINT表
strcpy(sql, "CREATE TABLE test_pt (");
strcat(sql, "id INTEGER NOT NULL PRIMARY KEY,");
strcat(sql, "name TEXT NOT NULL)");
ret = sqlite3_exec(db_handle, sql, NULL, NULL, &err_msg);
if (ret != SQLITE_OK)
{
fprintf(stderr, "Error: %s\n", err_msg);
sqlite3_free(err_msg);
goto stop;
}
/* creating a POINT Geometry column */
//创建一个POINT几何列
strcpy(sql, "SELECT AddGeometryColumn('test_pt', ");
strcat(sql, "'geom', 4326, 'POINT', 'XY')");
ret = sqlite3_exec(db_handle, sql, NULL, NULL, &err_msg);
if (ret != SQLITE_OK)
{
fprintf(stderr, "Error: %s\n", err_msg);
sqlite3_free(err_msg);
goto stop;
}

/* creating a LINESTRING table */
//创建一个 LINESTRING 表
strcpy(sql, "CREATE TABLE test_ln (");
strcat(sql, "id INTEGER NOT NULL PRIMARY KEY,");
strcat(sql, "name TEXT NOT NULL)");
ret = sqlite3_exec(db_handle, sql, NULL, NULL, &err_msg);
if (ret != SQLITE_OK)
{
fprintf(stderr, "Error: %s\n", err_msg);
sqlite3_free(err_msg);
goto stop;
}
/* creating a LINESTRING Geometry column */
//创建一个 LINESTRING几何列
strcpy(sql, "SELECT AddGeometryColumn('test_ln', ");
strcat(sql, "'geom', 4326, 'LINESTRING', 'XY')");
ret = sqlite3_exec(db_handle, sql, NULL, NULL, &err_msg);
if (ret != SQLITE_OK)
{
fprintf(stderr, "Error: %s\n", err_msg);
sqlite3_free(err_msg);
goto stop;
}

/* creating a POLYGON table */
//创建一个多边形表
strcpy(sql, "CREATE TABLE test_pg (");
strcat(sql, "id INTEGER NOT NULL PRIMARY KEY,");
strcat(sql, "name TEXT NOT NULL)");
ret = sqlite3_exec(db_handle, sql, NULL, NULL, &err_msg);
if (ret != SQLITE_OK)
{
fprintf(stderr, "Error: %s\n", err_msg);
sqlite3_free(err_msg);
goto stop;
}
/* creating a POLYGON Geometry column */
//创建一个多边形几何列
strcpy(sql, "SELECT AddGeometryColumn('test_pg', ");
strcat(sql, "'geom', 4326, 'POLYGON', 'XY')");
ret = sqlite3_exec(db_handle, sql, NULL, NULL, &err_msg);
if (ret != SQLITE_OK)
{
fprintf(stderr, "Error: %s\n", err_msg);
sqlite3_free(err_msg);
goto stop;
}

/*
* inserting some POINTs
* please note well: SQLite is ACID and Transactional
* so (to get best performance) the whole insert cycle
* will be handled as a single TRANSACTION
//插入一些POINTS
//请注意：SQLite是 ACID 和事务
//在整个循环中插入
//将作为一个单一的TRANSACTION处理
*/
ret = sqlite3_exec(db_handle, "BEGIN", NULL, NULL, &err_msg);
if (ret != SQLITE_OK)
{
fprintf(stderr, "Error: %s\n", err_msg);
sqlite3_free(err_msg);
goto stop;
}
for (i = 0; i < 100000; i++)
{
/* for POINTs we'll use full text sql statements */
strcpy(sql, "INSERT INTO test_pt (id, name, geom) VALUES (");
sprintf(sql2, "%d, 'test POINT #%d'", i + 1, i + 1);
strcat(sql, sql2);
sprintf(sql2, ", GeomFromText('POINT(%1.6f %1.6f)'", i / 1000.0,
i / 1000.0);
strcat(sql, sql2);
strcat(sql, ", 4326))");
ret = sqlite3_exec(db_handle, sql, NULL, NULL, &err_msg);
if (ret != SQLITE_OK)
{
fprintf(stderr, "Error: %s\n", err_msg);
sqlite3_free(err_msg);
goto stop;
}
}
ret = sqlite3_exec(db_handle, "COMMIT", NULL, NULL, &err_msg);
if (ret != SQLITE_OK)
{
fprintf(stderr, "Error: %s\n", err_msg);
sqlite3_free(err_msg);
goto stop;
}

/* checking POINTs */
strcpy(sql, "SELECT DISTINCT Count(*), ST_GeometryType(geom), ");
strcat(sql, "ST_Srid(geom) FROM test_pt");
ret =
sqlite3_get_table(db_handle, sql, &results, &rows, &columns, &err_msg);
if (ret != SQLITE_OK)
{
fprintf(stderr, "Error: %s\n", err_msg);
sqlite3_free(err_msg);
goto stop;
}
if (rows < 1)
{
fprintf(stderr, "Unexpected error: ZERO POINTs found ??????\n");
goto stop;
}
else
{
for (i = 1; i <= rows; i++)
{
cnt = atoi(results[(i * columns) + 0]);
type = results[(i * columns) + 1];
srid = atoi(results[(i * columns) + 2]);
fprintf(stderr, "Inserted %d entities of type %s SRID=%d\n",
cnt, type, srid);
}
}
sqlite3_free_table(results);

/*
* inserting some LINESTRINGs
* this time we'll use a Prepared Statement
*/
strcpy(sql, "INSERT INTO test_ln (id, name, geom) ");
strcat(sql, "VALUES (?, ?, GeomFromText(?, 4326))");
ret = sqlite3_prepare_v2(db_handle, sql, strlen(sql), &stmt, NULL);
if (ret != SQLITE_OK)
{
fprintf(stderr, "SQL error: %s\n%s\n", sql,
sqlite3_errmsg(db_handle));
goto stop;
}
ret = sqlite3_exec(db_handle, "BEGIN", NULL, NULL, &err_msg);
if (ret != SQLITE_OK)
{
fprintf(stderr, "Error: %s\n", err_msg);
sqlite3_free(err_msg);
goto stop;
}
for (i = 0; i < 100000; i++)
{
/* setting up values / binding */
sprintf(name, "test LINESTRING #%d", i + 1);
strcpy(geom, "LINESTRING(");
if ((i % 2) == 1)
{
/* odd row: five points */
strcat(geom, "-180.0 -90.0, ");
sprintf(sql2, "%1.6f %1.6f, ", -10.0 - (i / 1000.0),
-10.0 - (i / 1000.0));
strcat(geom, sql2);
sprintf(sql2, "%1.6f %1.6f, ", -10.0 - (i / 1000.0),
10.0 + (i / 1000.0));
strcat(geom, sql2);
sprintf(sql2, "%1.6f %1.6f, ", 10.0 + (i / 1000.0),
10.0 + (i / 1000.0));
strcat(geom, sql2);
strcat(geom, "180.0 90.0");
}
else
{
/* even row: two points */
sprintf(sql2, "%1.6f %1.6f, ", -10.0 - (i / 1000.0),
-10.0 - (i / 1000.0));
strcat(geom, sql2);
sprintf(sql2, "%1.6f %1.6f, ", 10.0 + (i / 1000.0),
10.0 + (i / 1000.0));
strcat(geom, sql2);
}
strcat(geom, ")");
sqlite3_reset(stmt);
sqlite3_clear_bindings(stmt);
sqlite3_bind_int(stmt, 1, i + 1);
sqlite3_bind_text(stmt, 2, name, strlen(name), SQLITE_STATIC);
sqlite3_bind_text(stmt, 3, geom, strlen(geom), SQLITE_STATIC);
/* performing INSERT INTO */
ret = sqlite3_step(stmt);
if (ret == SQLITE_DONE || ret == SQLITE_ROW)
continue;
fprintf(stderr, "sqlite3_step() error: [%s]\n",
sqlite3_errmsg(db_handle));
goto stop;
}
sqlite3_finalize(stmt);
ret = sqlite3_exec(db_handle, "COMMIT", NULL, NULL, &err_msg);
if (ret != SQLITE_OK)
{
fprintf(stderr, "Error: %s\n", err_msg);
sqlite3_free(err_msg);
goto stop;
}

/* checking LINESTRINGs */
strcpy(sql, "SELECT DISTINCT Count(*), ST_GeometryType(geom), ");
strcat(sql, "ST_Srid(geom) FROM test_ln");
ret =
sqlite3_get_table(db_handle, sql, &results, &rows, &columns, &err_msg);
if (ret != SQLITE_OK)
{
fprintf(stderr, "Error: %s\n", err_msg);
sqlite3_free(err_msg);
goto stop;
}
if (rows < 1)
{
fprintf(stderr, "Unexpected error: ZERO LINESTRINGs found ??????\n");
goto stop;
}
else
{
for (i = 1; i <= rows; i++)
{
cnt = atoi(results[(i * columns) + 0]);
type = results[(i * columns) + 1];
srid = atoi(results[(i * columns) + 2]);
fprintf(stderr, "Inserted %d entities of type %s SRID=%d\n",
cnt, type, srid);
}
}
sqlite3_free_table(results);

/*
* inserting some POLYGONs
* this time too we'll use a Prepared Statement
*/
strcpy(sql, "INSERT INTO test_pg (id, name, geom) ");
strcat(sql, "VALUES (?, ?, GeomFromText(?, 4326))");
ret = sqlite3_prepare_v2(db_handle, sql, strlen(sql), &stmt, NULL);
if (ret != SQLITE_OK)
{
fprintf(stderr, "SQL error: %s\n%s\n", sql,
sqlite3_errmsg(db_handle));
goto stop;
}
ret = sqlite3_exec(db_handle, "BEGIN", NULL, NULL, &err_msg);
if (ret != SQLITE_OK)
{
fprintf(stderr, "Error: %s\n", err_msg);
sqlite3_free(err_msg);
goto stop;
}
for (i = 0; i < 100000; i++)
{
/* setting up values / binding */
sprintf(name, "test POLYGON #%d", i + 1);
strcpy(geom, "POLYGON((");
sprintf(sql2, "%1.6f %1.6f, ", -10.0 - (i / 1000.0),
-10.0 - (i / 1000.0));
strcat(geom, sql2);
sprintf(sql2, "%1.6f %1.6f, ", 10.0 - (i / 1000.0),
-10.0 - (i / 1000.0));
strcat(geom, sql2);
sprintf(sql2, "%1.6f %1.6f, ", 10.0 + (i / 1000.0),
10.0 + (i / 1000.0));
strcat(geom, sql2);
sprintf(sql2, "%1.6f %1.6f, ", -10.0 - (i / 1000.0),
10.0 - (i / 1000.0));
strcat(geom, sql2);
sprintf(sql2, "%1.6f %1.6f", -10.0 - (i / 1000.0),
-10.0 - (i / 1000.0));
strcat(geom, sql2);
strcat(geom, "))");
sqlite3_reset(stmt);
sqlite3_clear_bindings(stmt);
sqlite3_bind_int(stmt, 1, i + 1);
sqlite3_bind_text(stmt, 2, name, strlen(name), SQLITE_STATIC);
sqlite3_bind_text(stmt, 3, geom, strlen(geom), SQLITE_STATIC);
/* performing INSERT INTO */
ret = sqlite3_step(stmt);
if (ret == SQLITE_DONE || ret == SQLITE_ROW)
continue;
fprintf(stderr, "sqlite3_step() error: [%s]\n",
sqlite3_errmsg(db_handle));
goto stop;
}
sqlite3_finalize(stmt);
ret = sqlite3_exec(db_handle, "COMMIT", NULL, NULL, &err_msg);
if (ret != SQLITE_OK)
{
fprintf(stderr, "Error: %s\n", err_msg);
sqlite3_free(err_msg);
goto stop;
}

/* checking POLYGONs */
strcpy(sql, "SELECT DISTINCT Count(*), ST_GeometryType(geom), ");
strcat(sql, "ST_Srid(geom) FROM test_pg");
ret =
sqlite3_get_table(db_handle, sql, &results, &rows, &columns, &err_msg);
if (ret != SQLITE_OK)
{
fprintf(stderr, "Error: %s\n", err_msg);
sqlite3_free(err_msg);
goto stop;
}
if (rows < 1)
{
fprintf(stderr, "Unexpected error: ZERO POLYGONs found ??????\n");
goto stop;
}
else
{
for (i = 1; i <= rows; i++)
{
cnt = atoi(results[(i * columns) + 0]);
type = results[(i * columns) + 1];
srid = atoi(results[(i * columns) + 2]);
fprintf(stderr, "Inserted %d entities of type %s SRID=%d\n",
cnt, type, srid);
}
}
sqlite3_free_table(results);

/* closing the DB connection */
stop:
sqlite3_close(db_handle);
return 0;
}