SQLite, version 3, is the file format used as the publicly documented native format for the SQLite database engine since June 2004. Software and associated documentation are available at https://www.sqlite.org/. The code, software, and accompanying documentation have been dedicated to the public domain. SQLite is an embedded SQL database engine that requires no configuration and reads and writes directly to ordinary disk files. A complete SQL database with tables, indexes, triggers, and views, is contained in a single disk file. The engine, and thus the file format, support a full-featured SQL implementation. The database file format, referred to here as 'SQLite_3', is cross-platform, transferable between 32-bit and 64-bit systems or between big-endian and little-endian architectures. These features make SQLite_3 a popular choice as an application file format. See Adoption under Sustainability Factors below for examples of the many operating systems and software applications in which it is distributed or used.
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May 28, 2021 Download SQLite Professional Read-Only 1.0.40 for Mac from our website for free. Our built-in antivirus scanned this Mac download and rated it as virus free. This free application is developed for Mac OS X 10.7 or later. The following version: 1.0 is the most frequently downloaded one by the program users. The program is included in Developer Tools. In August 2000, version 1.0 of SQLite was released, with storage based on gdbm (GNU Database Manager). SQLite 2.0 replaced gdbm with a custom B-tree implementation, adding transaction capability. SQLite 3.0, partially funded by America Online, added internationalization, manifest typing, and other major improvements. # Warning: `srcsqlite` was deprecated in dplyr 1.0.0. # Please use `tbl` directly with a database connection # This warning is displayed once every 8 hours. # Call `lifecycle::lastlifecyclewarnings` to see where this warning was generated. Currently, our new database is empty, it doesn’t contain any tables.
SQLite is not directly comparable to client/server SQL database engines such as MySQL, Oracle, PostgreSQL, or SQL Server. They are designed to implement a shared repository of enterprise data; SQLite is designed to provide local data storage for individual applications. See Appropriate Uses For SQLite for more detail on when SQLite is appropriate and examples of when a client/server SQL database engine would be more appropriate.
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The main SQLite_3 database file consists of one or more pages. All pages within the same database are the same size. The size of a page in bytes is a power of two between 512 and 65536 inclusive. The page size for a database file is indicated by the 2-byte integer located at an offset of 16 bytes from the beginning of the database file. The theoretical maximum size for an SQLite_3 database file is about 140 terabytes; typically, the file size limit of the underlying filesystem or hardware is the practical constraint. The smallest SQLite_3 database is a single 512-byte page.
Every page in an SQLite_3 database file is of a particular type:
- A b-tree page. The b-tree pages hold the main database content. Two kinds of b-trees are used by SQLite. The algorithm that Donald Knuth calls B*-Tree in 'The Art of Computer Programming' (Volume 3, Sorting and Searching) stores all data in the leaves of the tree. SQLite calls this variety of b-tree a table b-tree. A second b-tree variant storing only keys is used in SQLite_3 and called an index b-tree. Page 1 is a table b-tree page. A 100-byte database file header is found on page 1.
- A payload overflow page. When the payload of a b-tree cell is too large for the b-tree page, the surplus is spilled onto overflow pages. Overflow pages form a linked list.
- The lock-byte page. The lock-byte page was needed to support Win95. It is not needed for modern operating systems, but is retained for backwards compatibility.
- A freelist page. A database file may contain pages that are not in active use, for example, after information is deleted from the database. The freelist is a linked list of freelist trunk pages, each of which contains page numbers for zero or more freelist leaf pages. Unused pages are stored on the freelist and reused when required. A database may be configured for vacuuming to reduce or eliminate the freelist.
- A pointer map page. These are extra pages inserted into the database to make the operation of vacuuming more efficient.
Each ordinary SQL table in the database is represented by a table b-tree. Each entry in the table b-tree corresponds to a row of the SQL table. Row data is stored as records, each with a header that indicates the data type for each value in the row, followed by a sequence of values, usually one value for each column in the table.
The first 100 bytes of the database file act as a header. Header fields include a magic number; page size in bytes; fields relating to the number of pages of various types; a code indicating the encoding used for text data (UTF-8, UTF-16le [little-endian], or UTF-16be [big-endian]); minor version number [3.x.x] for the SQLite engine used to write the database file; a code to indicate whether the database is running with write ahead logging (WAL); and codes that indicate whether the database is configured for vacuuming.
Active7 months ago
I'm considering to use SQLite database for a C# application which deals with large volumes of data series. The data is currently in several CSV files of up to 20GBs in size each and of the following format:
2019.07.31 00:00:03.855,1.11568,1.11571,3,0
I was expecting to reduce the size considerably when migrating to SQLite but to some reason am getting some different results.
![Sqlite Sqlite](https://1.bp.blogspot.com/-V1t0RajjLBQ/YRjl2wv1ZwI/AAAAAAAAeMk/GpGGOmrFEfUSlRFX7oXlyeJrd1GaAwS_gCLcBGAsYHQ/s256/SQLite%2BExpert%2BProfessional%2BFull%2Bversion.png)
The example string in CSV format takes 44 bytes (43 chars + new line). As far as I understood the SQLite types definitions described at sqlite.org it should take about the same in the database:23 byte datetime text + 8*2 reals + 1*2 integers = 41 bytes
The dateTime can be stored as 8-byte integer (c# DateTime.Ticks) which should reduce the size to about 26 bytes per one line which is almost twice less than in CSV format.
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For an experiment I tried importing 142,157 lines of data. The CSV file is about 6kk bytes in size but the resulting DB file is about 5kk which is almost the same. Compression (available in DB Browser for SQLite) does not change anything.
The table schema is:
CREATE TABLE 'Data' ( 'dateTime' INTEGER, 'value1' REAL, 'value2' REAL, 'value3' INTEGER, 'value4' INTEGER )
An example row looks like this:
637001280038550000 1.11568 1.11571 3 0
Is it the SQLite internals which make that big overhead in size?How can I reduce the size?
As a side note, setting Primary Key on the dateTime field reduces the size of the example data file by 0.3kk bytes but adding unique constraint increases it by 3kk bytes making it about 8kk in total which is much bigger than the CSV one.
Update
So it turns out that the internals take 16%, PK takes additional 19% but still reduces the total size, and the unique contraint takes almost 40%!
The question remains valid. Is it possible to recude the size of the database or that is all one can get from it?
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yaugenka
yaugenkayaugenka
2There are some ways. Here are two that seem appropriate for your case:
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WITHOUT ROWID tables
The ROWID is an internal primary key that SQLite tables have by default, taking 64 bit per record. Since you were talking about a UNIQUE constraint for the datetime column, this column seems a good candidate for the primary key (which always has a unique constraint attached). So you can create a SQLite table without ROWID, as follows:
Storing delta values
I have never tried this in SQLite in practice, but: some data is more compactly stored by storing only the difference to the previous row. In this case, the datetime values are great for this, if they can be stored in order into the database. In that case, you would use three columns:
- A sequentially numbered integer primary key.
- A datetime integer column, only filled for every (say) 1000 records.
- A datetime_delta column, storing the difference from the last row with a filled datetime column.
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SQLite stores integer values individually into 2-9 bytes (incl. one storage mode byte), depending on their value. Assuming an average of 4 bytes for the sequential primary key and an average of 2.5 bytes for the delta values would save 2.5 bytes compared to the current 9 byte integer. Savings are larger if you have multiple columns in your table that profit from delta storage, as you need the sequential primary key only once. For example, if
value1
… value4
are measurement values that tend to grow and shrink over time, they are also good candidates.After loading a row at primary key value
n
, you would also have to retrieve the row at primary key value n DIV 1000
(meaning integer division) to have the base for your delta values.Professional1
taniustanius