# SQLite / Spatialite RDBMS

Driver short name

SQLite

Build dependencies

libsqlite3 or libspatialite

OGR optionally supports spatial and non-spatial tables stored in SQLite 3.x database files. SQLite is a "light weight" single file based RDBMS engine with fairly complete SQL semantics and respectable performance.

The driver can handle "regular" SQLite databases, as well as Spatialite databases (spatial enabled SQLite databases). The type of an existing database can be checked from the SQLITE debug info value "OGR style SQLite DB found/ SpatiaLite DB found/SpatiaLite v4 DB found" obtained by running `ogrinfo db.sqlite --debug on`

Starting with GDAL 2.2, the SQLite driver can also read databases with RasterLite2 raster coverages.

The SQLite database is essentially typeless, but the SQLite driver will attempt to classify attributes field as text, integer or floating point based on the contents of the first record in a table. Datetime field types are also handled.

Starting with GDAL 2.2, the "JSonStringList", "JSonIntegerList", "JSonInteger64List" and "JSonRealList" SQLite declaration types are used to map the corresponding OGR StringList, IntegerList, Integer64List and RealList types. The field values are then encoded as JSon arrays, with proper CSV escaping.

SQLite databases often do not work well over NFS, or some other networked file system protocols due to the poor support for locking. It is safest to operate only on SQLite files on a physical disk of the local system.

SQLite is an optionally compiled in driver. It is not compiled in by default.

By default, SQL statements are passed directly to the SQLite database engine. It's also possible to request the driver to handle SQL commands with OGR SQL engine, by passing "OGRSQL" string to the ExecuteSQL() method, as name of the SQL dialect.

The `OGR_SQLITE_SYNCHRONOUS` configuration option has been added. When set to OFF, this issues a 'PRAGMA synchronous = OFF' command to the SQLite database. This has the advantage of speeding-up some write operations (e.g. on EXT4 filesystems), but at the expense of data safety w.r.t system/OS crashes. So use it carefully in production environments and read the SQLite related documentation.

Any SQLite pragma can be specified with the `OGR_SQLITE_PRAGMA` configuration option. The syntax is `OGR_SQLITE_PRAGMA = "pragma_name=pragma_value[,pragma_name2=pragma_value2]*"`.

## Driver capabilities

Supports Create()

This driver supports the `GDALDriver::Create()` operation

Supports Georeferencing

This driver supports georeferencing

Supports VirtualIO

This driver supports virtual I/O operations (/vsimem/, etc.)

## "Regular" SQLite databases

The driver looks for a geometry_columns table laid out as defined loosely according to OGC Simple Features standards, particularly as defined in FDO RFC 16. If found it is used to map tables to layers.

If geometry_columns is not found, each table is treated as a layer. Layers with a WKT_GEOMETRY field will be treated as spatial tables, and the WKT_GEOMETRY column will be read as Well Known Text geometry.

If geometry_columns is found, it will be used to lookup spatial reference systems in the spatial_ref_sys table.

While the SQLite driver supports reading spatial data from records, there is no support for spatial indexing, so spatial queries will tend to be slow (use Spatialite for that). Attributes queries may be fast, especially if indexes are built for appropriate attribute columns using the "CREATE INDEX ON ( )" SQL command.

The driver also supports reading and writing the following non-linear geometry types :CIRCULARSTRING, COMPOUNDCURVE, CURVEPOLYGON, MULTICURVE and MULTISURFACE. Note: this is not true for Spatialite databases, since those geometry types are not supported by current Spatialite versions.

## Tables with multiple geometry columns

Layers with multiple geometry columns can be created, modified or read, following new API described in RFC 41 : Support for multiple geometry fields in OGR

## REGEXP operator

By default, the REGEXP operator has no implementation in SQLite. With OGRbuilt against the PCRE library, the REGEXP operator is available in SQL statements run by OGR.

## Using the SpatiaLite library (Spatial extension for SQLite)

The SQLite driver can read and write SpatiaLite databases. Creating or updating a spatialite database requires explicit linking against SpatiaLite library (version >= 2.3.1). Explicit linking against SpatiaLite library also provides access to functions provided by this library, such as spatial indexes, spatial functions, etc...

A few examples :

    # Duplicate the sample database provided with SpatiaLite
    ogr2ogr -f SQLite testspatialite.sqlite test-2.3.sqlite  -dsco SPATIALITE=YES

    # Make a request with a spatial filter. Will work faster if spatial index has
    # been created and explicit linking against SpatiaLite library.
    ogrinfo testspatialite.sqlite Towns -spat 754000 4692000 770000 4924000

## Opening with 'VirtualShape:'

(Require Spatialite support)

It is possible to open on-the-fly a shapefile as a VirtualShape with Spatialite. The syntax to use for the datasource is "VirtualShape:/path/to/shapefile.shp" (the shapefile must be a "real" file).

This gives the capability to use the spatial operations of Spatialite (note that spatial indexes on virtual tables are not available).

## The SQLite SQL dialect

The SQLite SQL engine can be used to run SQL queries on any OGR datasource if using the SQL SQLite dialect.

## The VirtualOGR SQLite extension

The GDAL/OGR library can be loaded as a SQLite extension. The extension is loaded with the load_extension(gdal_library_name) SQL function, where gdal_library_name is typically libgdal.so on Unix/Linux, gdal110.dll on Windows, etc..

After the extension is loaded, a virtual table, corresponding to a OGR layer, can be created with one of the following SQL statement :

    CREATE VIRTUAL TABLE table_name USING VirtualOGR(datasource_name);
    CREATE VIRTUAL TABLE table_name USING VirtualOGR(datasource_name, update_mode);
    CREATE VIRTUAL TABLE table_name USING VirtualOGR(datasource_name, update_mode, layer_name);
    CREATE VIRTUAL TABLE table_name USING VirtualOGR(datasource_name, update_mode, layer_name, expose_ogr_style);

where :

- datasource_name is the connection string to any OGR datasource.

- update_mode = 0 for read-only mode (default value) or 1 for update mode.

- layer_name = the name of a layer of the opened datasource.

- expose_ogr_style = 0 to prevent the OGR_STYLE special from being displayed (default value) or 1 to expose it.

Note: layer_name does not need to be specified if the datasource has only one single layer.

From the sqlite3 console, a typical use case is :

    sqlite> SELECT load_extension('libgdal.so');

    sqlite> SELECT load_extension('mod_spatialite.so');

    sqlite> CREATE VIRTUAL TABLE poly USING VirtualOGR('poly.shp');

    sqlite> SELECT *, ST_Area(GEOMETRY) FROM POLY;
    215229.266|168.0|35043411||215229.265625
    247328.172|179.0|35043423||247328.171875
    261752.781|171.0|35043414||261752.78125
    547597.188|173.0|35043416||547597.2109375
    15775.758|172.0|35043415||15775.7578125
    101429.977|169.0|35043412||101429.9765625
    268597.625|166.0|35043409||268597.625
    1634833.375|158.0|35043369||1634833.390625
    596610.313|165.0|35043408||596610.3359375
    5268.813|170.0|35043413||5268.8125

Alternatively, you can use the ogr_datasource_load_layers(datasource_name[, update_mode[, prefix]]) function to automatically load all the layers of a datasource.

    sqlite> SELECT load_extension('libgdal.so');

    sqlite> SELECT load_extension('mod_spatialite.so');

    sqlite> SELECT ogr_datasource_load_layers('poly.shp');
    1
    sqlite> SELECT * FROM sqlite_master;
    table|poly|poly|0|CREATE VIRTUAL TABLE "poly" USING VirtualOGR('poly.shp', 0, 'poly')

Refer to the SQL SQLite dialect for an overview of the capabilities of VirtualOGR tables.

## Creation Issues

The SQLite driver supports creating new SQLite database files, or adding tables to existing ones.

### Transaction support

The driver implements transactions at the database level, per RFC 54: Dataset transactions

## Relationships

New in version 3.6.

Relationship retrieval is supported. Relationships will be reported for tables which utilize FOREIGN KEY constraints.

Relationship creation is supported since GDAL 3.7, for one-to-many relationships only.

### Dataset open options

- LIST_ALL_TABLES=[YES/NO]: This may be "YES" to force all tables, including non-spatial ones, to be listed.

- LIST_VIRTUAL_OGR=[YES/NO]: This may be "YES" to force VirtualOGR virtual tables to be listed. This should only be enabled on trusted datasources to avoid potential safety issues.

- PRELUDE_STATEMENTS=value: (GDAL >= 3.2) SQL statement(s) to send on the SQLite3 connection before any other ones. In case of several statements, they must be separated with the semi-column (;) sign. This option may be useful to attach another database to the current one and issue cross-database requests.

  Note

  The other database must be of a type recognized by this driver, so its geometry blobs are properly recognized (so typically not a GeoPackage one)

### Database creation options

- METADATA=[YES/NO]: This can be used to avoid creating the geometry_columns and spatial_ref_sys tables in a new database. By default these metadata tables are created when a new database is created.

- SPATIALITE=[YES/NO]: Create the SpatiaLite flavor of the metadata tables, which are a bit differ from the metadata used by this OGR driver and from OGC specifications. Implies `METADATA=YES`.

  Please note: OGR must be linked against libspatialite in order to support insert/write on SpatiaLite; if not, read-only mode is enforced.

  Attempting to perform any insert/write on SpatiaLite skipping the appropriate library support simply produces broken (corrupted) DB-files.

  Important notice: when the underlying libspatialite is v.2.3.1 (or any previous version) any Geometry will be casted to 2D [XY], because earlier versions of this library are simply able to support 2D [XY] dimensions. Version 2.4.0 (or any subsequent) is required in order to support 2.5D [XYZ].

- INIT_WITH_EPSG=[YES/NO]: Insert the content of the EPSG CSV files into the spatial_ref_sys table. Defaults to NO for regular SQLite databases. Please note: if `SPATIALITE=YES` and the underlying libspatialite is v2.4 or v3.X, `INIT_WITH_EPSG` is ignored; those library versions will unconditionally load the EPSG dataset into the spatial_ref_sys table when creating a new DB (self-initialization). Starting with libspatialite 4.0, `INIT_WITH_EPSG` defaults to YES, but can be set to NO.

### Layer creation options

- FORMAT=[WKB/WKT/SPATIALITE]: Defaults to `WKB`. Controls the format used for the geometry column. By default WKB (Well Known Binary) is used. This is generally more space and processing efficient, but harder to inspect or use in simple applications than WKT (Well Known Text). SpatiaLite extension uses its own binary format to store geometries and you can choose it as well. It will be selected automatically when SpatiaLite database is opened or created with `SPATIALITE=YES` option. SPATIALITE value is available.

- GEOMETRY_NAME=value: By default OGR creates new tables with the geometry column named GEOMETRY (or WKT_GEOMETRY if `FORMAT=WKT`). If you wish to use a different name, it can be supplied with the `GEOMETRY_NAME` layer creation option.

- LAUNDER=[YES/NO]: Defaults to `YES`. Controls whether layer and field names will be laundered for easier use in SQLite. Laundered names will be converted to lower case and some special characters(' - #) will be changed to underscores.

- SPATIAL_INDEX=[YES/NO]: Defaults to `YES`. If the database is of the SpatiaLite flavor, and if OGR is linked against libspatialite, this option can be used to control if a spatial index must be created.

- COMPRESS_GEOM=[YES/NO]: Defaults to `NO`. If the format of the geometry BLOB is of the SpatiaLite flavor, this option can be used to control if the compressed format for geometries (LINESTRINGs, POLYGONs) must be used. This format is understood by Spatialite v2.4 (or any subsequent version). Default to NO. Note: when updating an existing Spatialite DB, the `COMPRESS_GEOM` configuration option can be set to produce similar results for appended/overwritten features.

- SRID=value: Used to force the SRID number of the SRS associated with the layer. When this option isn't specified and that a SRS is associated with the layer, a search is made in the spatial_ref_sys to find a match for the SRS, and, if there is no match, a new entry is inserted for the SRS in the spatial_ref_sys table. When the SRID option is specified, this search (and the eventual insertion of a new entry) will not be done : the specified SRID is used as such.

- COMPRESS_COLUMNS=<column_name1[,column_name2, ...]>: A list of (String) columns that must be compressed with ZLib DEFLATE algorithm. This might be beneficial for databases that have big string blobs. However, use with care, since the value of such columns will be seen as compressed binary content with other SQLite utilities (or previous OGR versions). With OGR, when inserting, modifying or querying compressed columns, compression/decompression is done transparently. However, such columns cannot be (easily) queried with an attribute filter or WHERE clause. Note: in table definition, such columns have the "VARCHAR_deflate" declaration type.

- FID=value: Defaults to `OGC_FID`. Name of the FID column to create.

- STRICT=[YES/NO]: (GDAL >= 3.3.5) Defaults to `NO`. (SQLite >= 3.37) Whether the table should be created as a strict table, that is strong column type checking. This normally has little influence when operating only through OGR, since it has typed columns, but can help to strengthen database integrity when the database might be edited by external tools. Note that databases that contain STRICT tables can only be read by SQLite >= 3.37. The set of column data types supported in STRICT mode is: Integer, Integer64, Real, String, DateTime, Date and Time. The `COMPRESS_COLUMNS` option is ignored in strict mode.

## Configuration options

The following configuration options are available:

- SQLITE_LIST_ALL_TABLES=[YES/NO]: Defaults to `NO`. Set to "YES" to list all tables (not just the tables listed in the geometry_columns table). This can also be done using the `LIST_ALL_TABLES` open option.

- OGR_PROMOTE_TO_INTEGER64=[YES/NO]: Defaults to `NO`. Whether to read fields with type `INTEGER` as 64-bit integers.

- OGR_SQLITE_LIST_VIRTUAL_OGR=[YES/NO]: Defaults to `NO`. Set to "YES" to list VirtualOGR layers. Defaults to "NO" as there might be some security implications if a user is provided with a file and doesn't know that there are virtual OGR tables in it.

- OGR_SQLITE_JOURNAL=value: can be used to set the journal mode of the SQLite file, see also https://www.sqlite.org/pragma.html#pragma_journal_mode.

- OGR_SQLITE_CACHE=value: see Performance hints.

- OGR_SQLITE_SYNCHRONOUS=value: see Performance hints.

- OGR_SQLITE_LOAD_EXTENSIONS=[<extension1,...,extensionN>/ENABLE_SQL_LOAD_EXTENSION]: (GDAL >= 3.5.0) Comma separated list of names of shared libraries containing extensions to load at database opening. If a file cannot be loaded directly, attempts are made to load with various operating-system specific extensions added. So for example, if "samplelib" cannot be loaded, then names like "samplelib.so" or "samplelib.dylib" or "samplelib.dll" might be tried also. The special value `ENABLE_SQL_LOAD_EXTENSION` can be used to enable the use of the SQL `load_extension()` function, which is normally disabled in standard builds of sqlite3. Loading extensions as a potential security impact if they are untrusted.

- OGR_SQLITE_PRAGMA=value: with this option any SQLite pragma can be specified. The syntax is `OGR_SQLITE_PRAGMA = "pragma_name=pragma_value[,pragma_name2=pragma_value2]*"`.

- SQLITE_USE_OGR_VFS=[YES/NO]: YES enables extra buffering/caching by the GDAL/OGR I/O layer and can speed up I/O. More information here. Be aware that no file locking will occur if this option is activated, so concurrent edits may lead to database corruption.

- COMPRESS_GEOM=[YES/NO]: Defaults to `NO`. Equivalent of `COMPRESS_GEOM` layer creation option for use when updating or appending to an existing layer.

## Performance hints

SQLite is a Transactional DBMS; while many INSERT statements are executed in close sequence, BEGIN TRANSACTION and COMMIT TRANSACTION statements have to be invoked appropriately (with the OGR_L_StartTransaction() / OGR_L_CommitTransaction()) in order to get optimal performance. By default, if no transaction is explicitly started, SQLite will autocommit on every statement, which will be slow. If using ogr2ogr, its default behavior is to COMMIT a transaction every 20000 inserted rows. The -gt argument allows explicitly setting the number of rows for each transaction. Increasing to -gt 65536 or more ensures optimal performance while populating some table containing many hundredth thousand or million rows.

SQLite usually has a very minimal memory foot-print; just about 20MB of RAM are reserved to store the internal Page Cache [merely 2000 pages]. This value too may well be inappropriate under many circumstances, most notably when accessing some really huge DB-file containing many tables related to a corresponding Spatial Index. Explicitly setting a much more generously dimensioned internal Page Cache may often help to get a noticeably better performance. You can explicitly set the internal Page Cache size using the configuration option `OGR_SQLITE_CACHE` value [value being measured in MB]; if your HW has enough available RAM, defining a Cache size as big as 512MB (or even 1024MB) may sometimes help a lot in order to get better performance.

Setting the `OGR_SQLITE_SYNCHRONOUS` configuration option to OFF might also increase performance when creating SQLite databases (although at the expense of integrity in case of interruption/crash ).

If many source files will be collected into the same Spatialite table, it can be much faster to initialize the table without a spatial index by using -lco `SPATIAL_INDEX=NO` and to create spatial index with a separate command after all the data are appended. Spatial index can be created with ogrinfo command

    ogr2ogr -f SQLite -dsco SPATIALITE=YES db.sqlite first.shp -nln the_table -lco SPATIAL_INDEX=NO
    ogr2ogr -append db.sqlite second.shp -nln the_table
    ...
    ogr2ogr -append db.sqlite last.shp -nln the_table
    ogrinfo db.sqlite -sql "SELECT CreateSpatialIndex('the_table','GEOMETRY')"

If a database has gone through editing operations, it might be useful to run a VACUUM query to compact and optimize it.

    ogrinfo db.sqlite -sql "VACUUM"

## Example

- Convert a non-spatial SQLite table into a GeoPackage:

    ogr2ogr \
      -f "GPKG" output.gpkg \
      input.sqlite \
      -sql \
      "SELECT
         *,
         MakePoint(longitude, latitude, 4326) AS geometry
       FROM
         my_table" \
      -nln "location" \
      -s_srs "EPSG:4326"

- Perform a join between 2 SQLite/Spatialite databases:

    ogrinfo my_spatial.db \
        -sql "SELECT poly.id, other.foo FROM poly JOIN other_schema.other USING (id)" \
        -oo PRELUDE_STATEMENTS="ATTACH DATABASE 'other.db' AS other_schema"

## Credits

- Development of the OGR SQLite driver was supported by DM Solutions Group and GoMOOS.

- Full support for SpatiaLite was contributed by A.Furieri, with funding from Regione Toscana

## Links

- http://www.sqlite.org: Main SQLite page.

- https://www.gaia-gis.it/fossil/libspatialite/index: SpatiaLite extension to SQLite.

- FDO RFC 16: FDO Provider for SQLite

- RasterLite2 driver