Tracker is implemented on top of SQLite, and all of its benefits and limits apply. This document will break down how those limits apply to Tracker. Depending on your distributor, the limits might be changed via SQLite build-time options.
Maximum string length
Tracker can store by default up to 1 GiB in a text field by default. This
limit is controlled by
Maximum number of properties and select columns
The maximum amount of properties in the domain of a single class, and
the maximum number of global fulltext-search properties in the ontology
are limited by
SQLITE_MAX_COLUMN (defaults to 2000).
Each column in the result set of a SELECT query contains additional
information included as an additional column, so the limit of columns
that can be retrieved in a single SELECT query is effectively half
SQLITE_MAX_COLUMN (1000 with the default settings).
Underlying parser limits
SQLite defines some limits to its parser. Maximum query length is 1 MiB,
its maximum expression tree depth is 1000, and it allows up to 500
UNION / INTERSECT / EXCEPT statements.
There is no straightforward relation between the SPARQL query and the SQL one, so it is undefined how this limit applies to SPARQL queries. Query and ontology simplifications may help reduce its likelyhood.
These SQLite limits are controlled by
SQLITE_MAX_COMPOUND_SELECT. The SPARQL parser
is not affected in itself by these limits.
Maximum number of tables in a
SQLite does not allow Join operations containing more than 64 tables. This limit may impact complex Tracker queries in various ways, most likely culprits are operations across the whole union graph, and access to multi-valued properties.
Such queries can be tweaked (e.g. specifying a graph, or reducing the amount of accessed properties) or split into multiple ones to bypass this limit.
Maximum number or arguments in a function
SQLite defines a limit of 100, controlled by
This affects all builtin and extra functions with variable arguments,
Limits on the number of graphs
SQLite has a limit on the number of databases that can be attached,
SQLITE_MAX_LIMIT_ATTACHED (defaults to 10, maximum 128).
Tracker uses attached databases to implement its support for multiple graphs, so the maximum amount of graphs for a given TrackerSparqlConnection is equally restricted.
Limits on glob search
SQLite defines a maximum length of 50 KiB for GLOB patterns. This
CONTAINS / STRSTARTS / STRENDS.
Limits on the number of parameters in a statement
SQLite defines a maximum of 999 parameters to be passed as arguments
to a statement, controlled by
TrackerSparqlStatement has the same limit.
Maximum number of pages in a database
SQLite sets a default restriction of 1073741823 pages to database file size (about 8 TB with Tracker settings). This limit applies per graph.
Type formats and precision
Integers are 64 bit wide. Floating point numbers have IEEE764 double precision. Dates/times have microsecond precision, and may range between 0001-01-01 00:00:00 and 9999-12-31 23:59:59.
The results of the search are