360 lines
17 KiB
Markdown
360 lines
17 KiB
Markdown
<h1 align="center">SQLite Source Repository</h1>
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This repository contains the complete source code for the
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[SQLite database engine](https://sqlite.org/). Some test scripts
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are also included. However, many other test scripts
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and most of the documentation are managed separately.
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## Version Control
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SQLite sources are managed using
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[Fossil](https://www.fossil-scm.org/), a distributed version control system
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that was specifically designed and written to support SQLite development.
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The [Fossil repository](https://sqlite.org/src/timeline) contains the urtext.
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If you are reading this on GitHub or some other Git repository or service,
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then you are looking at a mirror. The names of check-ins and
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other artifacts in a Git mirror are different from the official
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names for those objects. The official names for check-ins are
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found in a footer on the check-in comment for authorized mirrors.
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The official check-in name can also be seen in the `manifest.uuid` file
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in the root of the tree. Always use the official name, not the
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Git-name, when communicating about an SQLite check-in.
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If you pulled your SQLite source code from a secondary source and want to
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verify its integrity, there are hints on how to do that in the
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[Verifying Code Authenticity](#vauth) section below.
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## Contacting The SQLite Developers
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The preferred way to ask questions or make comments about SQLite or to
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report bugs against SQLite is to visit the
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[SQLite Forum](https://sqlite.org/forum) at <https://sqlite.org/forum/>.
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Anonymous postings are permitted.
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If you think you have found a bug that has security implications and
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you do not want to report it on the public forum, you can send a private
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email to drh at sqlite dot org.
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## Public Domain
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The SQLite source code is in the public domain. See
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<https://sqlite.org/copyright.html> for details.
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Because SQLite is in the public domain, we do not normally accept pull
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requests, because if we did take a pull request, the changes in that
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pull request might carry a copyright and the SQLite source code would
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then no longer be fully in the public domain.
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## Obtaining The SQLite Source Code
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If you do not want to use Fossil, you can download tarballs or ZIP
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archives or [SQLite archives](https://sqlite.org/cli.html#sqlar) as follows:
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* Latest trunk check-in as
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[Tarball](https://www.sqlite.org/src/tarball/sqlite.tar.gz),
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[ZIP-archive](https://www.sqlite.org/src/zip/sqlite.zip), or
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[SQLite-archive](https://www.sqlite.org/src/sqlar/sqlite.sqlar).
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* Latest release as
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[Tarball](https://www.sqlite.org/src/tarball/sqlite.tar.gz?r=release),
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[ZIP-archive](https://www.sqlite.org/src/zip/sqlite.zip?r=release), or
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[SQLite-archive](https://www.sqlite.org/src/sqlar/sqlite.sqlar?r=release).
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* For other check-ins, substitute an appropriate branch name or
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tag or hash prefix in place of "release" in the URLs of the previous
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bullet. Or browse the [timeline](https://www.sqlite.org/src/timeline)
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to locate the check-in desired, click on its information page link,
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then click on the "Tarball" or "ZIP Archive" links on the information
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page.
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If you do want to use Fossil to check out the source tree,
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first install Fossil version 2.0 or later.
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(Source tarballs and precompiled binaries available
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[here](https://www.fossil-scm.org/fossil/uv/download.html). Fossil is
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a stand-alone program. To install, simply download or build the single
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executable file and put that file someplace on your $PATH.)
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Then run commands like this:
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mkdir -p ~/sqlite ~/Fossils
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cd ~/sqlite
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fossil clone https://www.sqlite.org/src ~/Fossils/sqlite.fossil
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fossil open ~/Fossils/sqlite.fossil
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After setting up a repository using the steps above, you can always
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update to the latest version using:
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fossil update trunk ;# latest trunk check-in
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fossil update release ;# latest official release
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Or type "fossil ui" to get a web-based user interface.
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## Compiling for Unix-like systems
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First create a directory in which to place
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the build products. It is recommended, but not required, that the
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build directory be separate from the source directory. Cd into the
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build directory and then from the build directory run the configure
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script found at the root of the source tree. Then run "make".
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For example:
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tar xzf sqlite.tar.gz ;# Unpack the source tree into "sqlite"
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mkdir bld ;# Build will occur in a sibling directory
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cd bld ;# Change to the build directory
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../sqlite/configure ;# Run the configure script
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make ;# Builds the "sqlite3" command-line tool
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make sqlite3.c ;# Build the "amalgamation" source file
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make devtest ;# Run some tests (requires Tcl)
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See the makefile for additional targets.
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The configure script uses autoconf 2.61 and libtool. If the configure
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script does not work out for you, there is a generic makefile named
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"Makefile.linux-gcc" in the top directory of the source tree that you
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can copy and edit to suit your needs. Comments on the generic makefile
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show what changes are needed.
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## Compiling for Windows Using MSVC
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On Windows, all applicable build products can be compiled with MSVC.
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You will also need a working installation of TCL.
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See the [compile-for-windows.md](doc/compile-for-windows.md) document for
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additional information about how to install MSVC and TCL and configure your
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build environment.
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If you want to run tests, you need to let SQLite know the location of your
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TCL library, using a command like this:
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set TCLDIR=c:\Tcl
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SQLite uses "tclsh.exe" as part of the build process, and so that utility
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program will need to be somewhere on your %PATH%. The finished SQLite library
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does not contain any TCL code, but it does use TCL to help with the build process
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and to run tests.
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Build using Makefile.msc. Example:
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nmake /f Makefile.msc
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nmake /f Makefile.msc sqlite3.c
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nmake /f Makefile.msc devtest
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nmake /f Makefile.msc releasetest
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There are many other makefile targets. See comments in Makefile.msc for
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details.
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## Source Code Tour
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Most of the core source files are in the **src/** subdirectory. The
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**src/** folder also contains files used to build the "testfixture" test
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harness. The names of the source files used by "testfixture" all begin
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with "test".
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The **src/** also contains the "shell.c" file
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which is the main program for the "sqlite3.exe"
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[command-line shell](https://sqlite.org/cli.html) and
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the "tclsqlite.c" file which implements the
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[Tcl bindings](https://sqlite.org/tclsqlite.html) for SQLite.
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(Historical note: SQLite began as a Tcl
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extension and only later escaped to the wild as an independent library.)
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Test scripts and programs are found in the **test/** subdirectory.
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Additional test code is found in other source repositories.
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See [How SQLite Is Tested](https://www.sqlite.org/testing.html) for
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additional information.
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The **ext/** subdirectory contains code for extensions. The
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Full-text search engine is in **ext/fts3**. The R-Tree engine is in
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**ext/rtree**. The **ext/misc** subdirectory contains a number of
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smaller, single-file extensions, such as a REGEXP operator.
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The **tool/** subdirectory contains various scripts and programs used
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for building generated source code files or for testing or for generating
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accessory programs such as "sqlite3_analyzer(.exe)".
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### Generated Source Code Files
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Several of the C-language source files used by SQLite are generated from
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other sources rather than being typed in manually by a programmer. This
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section will summarize those automatically-generated files. To create all
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of the automatically-generated files, simply run "make target_source".
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The "target_source" make target will create a subdirectory "tsrc/" and
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fill it with all the source files needed to build SQLite, both
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manually-edited files and automatically-generated files.
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The SQLite interface is defined by the **sqlite3.h** header file, which is
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generated from src/sqlite.h.in, ./manifest.uuid, and ./VERSION. The
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[Tcl script](https://www.tcl.tk) at tool/mksqlite3h.tcl does the conversion.
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The manifest.uuid file contains the SHA3 hash of the particular check-in
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and is used to generate the SQLITE\_SOURCE\_ID macro. The VERSION file
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contains the current SQLite version number. The sqlite3.h header is really
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just a copy of src/sqlite.h.in with the source-id and version number inserted
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at just the right spots. Note that comment text in the sqlite3.h file is
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used to generate much of the SQLite API documentation. The Tcl scripts
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used to generate that documentation are in a separate source repository.
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The SQL language parser is **parse.c** which is generated from a grammar in
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the src/parse.y file. The conversion of "parse.y" into "parse.c" is done
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by the [lemon](./doc/lemon.html) LALR(1) parser generator. The source code
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for lemon is at tool/lemon.c. Lemon uses the tool/lempar.c file as a
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template for generating its parser.
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Lemon also generates the **parse.h** header file, at the same time it
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generates parse.c.
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The **opcodes.h** header file contains macros that define the numbers
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corresponding to opcodes in the "VDBE" virtual machine. The opcodes.h
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file is generated by scanning the src/vdbe.c source file. The
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Tcl script at ./mkopcodeh.tcl does this scan and generates opcodes.h.
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A second Tcl script, ./mkopcodec.tcl, then scans opcodes.h to generate
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the **opcodes.c** source file, which contains a reverse mapping from
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opcode-number to opcode-name that is used for EXPLAIN output.
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The **keywordhash.h** header file contains the definition of a hash table
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that maps SQL language keywords (ex: "CREATE", "SELECT", "INDEX", etc.) into
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the numeric codes used by the parse.c parser. The keywordhash.h file is
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generated by a C-language program at tool mkkeywordhash.c.
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The **pragma.h** header file contains various definitions used to parse
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and implement the PRAGMA statements. The header is generated by a
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script **tool/mkpragmatab.tcl**. If you want to add a new PRAGMA, edit
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the **tool/mkpragmatab.tcl** file to insert the information needed by the
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parser for your new PRAGMA, then run the script to regenerate the
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**pragma.h** header file.
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### The Amalgamation
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All of the individual C source code and header files (both manually-edited
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and automatically-generated) can be combined into a single big source file
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**sqlite3.c** called "the amalgamation". The amalgamation is the recommended
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way of using SQLite in a larger application. Combining all individual
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source code files into a single big source code file allows the C compiler
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to perform more cross-procedure analysis and generate better code. SQLite
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runs about 5% faster when compiled from the amalgamation versus when compiled
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from individual source files.
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The amalgamation is generated from the tool/mksqlite3c.tcl Tcl script.
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First, all of the individual source files must be gathered into the tsrc/
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subdirectory (using the equivalent of "make target_source") then the
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tool/mksqlite3c.tcl script is run to copy them all together in just the
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right order while resolving internal "#include" references.
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The amalgamation source file is more than 200K lines long. Some symbolic
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debuggers (most notably MSVC) are unable to deal with files longer than 64K
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lines. To work around this, a separate Tcl script, tool/split-sqlite3c.tcl,
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can be run on the amalgamation to break it up into a single small C file
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called **sqlite3-all.c** that does #include on about seven other files
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named **sqlite3-1.c**, **sqlite3-2.c**, ..., **sqlite3-7.c**. In this way,
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all of the source code is contained within a single translation unit so
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that the compiler can do extra cross-procedure optimization, but no
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individual source file exceeds 32K lines in length.
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## How It All Fits Together
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SQLite is modular in design.
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See the [architectural description](https://www.sqlite.org/arch.html)
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for details. Other documents that are useful in
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(helping to understand how SQLite works include the
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[file format](https://www.sqlite.org/fileformat2.html) description,
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the [virtual machine](https://www.sqlite.org/opcode.html) that runs
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prepared statements, the description of
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[how transactions work](https://www.sqlite.org/atomiccommit.html), and
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the [overview of the query planner](https://www.sqlite.org/optoverview.html).
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Years of effort have gone into optimizing SQLite, both
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for small size and high performance. And optimizations tend to result in
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complex code. So there is a lot of complexity in the current SQLite
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implementation. It will not be the easiest library in the world to hack.
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Key files:
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* **sqlite.h.in** - This file defines the public interface to the SQLite
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library. Readers will need to be familiar with this interface before
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trying to understand how the library works internally.
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* **sqliteInt.h** - this header file defines many of the data objects
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used internally by SQLite. In addition to "sqliteInt.h", some
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subsystems have their own header files.
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* **parse.y** - This file describes the LALR(1) grammar that SQLite uses
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to parse SQL statements, and the actions that are taken at each step
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in the parsing process.
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* **vdbe.c** - This file implements the virtual machine that runs
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prepared statements. There are various helper files whose names
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begin with "vdbe". The VDBE has access to the vdbeInt.h header file
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which defines internal data objects. The rest of SQLite interacts
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with the VDBE through an interface defined by vdbe.h.
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* **where.c** - This file (together with its helper files named
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by "where*.c") analyzes the WHERE clause and generates
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virtual machine code to run queries efficiently. This file is
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sometimes called the "query optimizer". It has its own private
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header file, whereInt.h, that defines data objects used internally.
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* **btree.c** - This file contains the implementation of the B-Tree
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storage engine used by SQLite. The interface to the rest of the system
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is defined by "btree.h". The "btreeInt.h" header defines objects
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used internally by btree.c and not published to the rest of the system.
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* **pager.c** - This file contains the "pager" implementation, the
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module that implements transactions. The "pager.h" header file
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defines the interface between pager.c and the rest of the system.
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* **os_unix.c** and **os_win.c** - These two files implement the interface
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between SQLite and the underlying operating system using the run-time
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pluggable VFS interface.
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* **shell.c.in** - This file is not part of the core SQLite library. This
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is the file that, when linked against sqlite3.a, generates the
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"sqlite3.exe" command-line shell. The "shell.c.in" file is transformed
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into "shell.c" as part of the build process.
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* **tclsqlite.c** - This file implements the Tcl bindings for SQLite. It
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is not part of the core SQLite library. But as most of the tests in this
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repository are written in Tcl, the Tcl language bindings are important.
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* **test\*.c** - Files in the src/ folder that begin with "test" go into
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building the "testfixture.exe" program. The testfixture.exe program is
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an enhanced Tcl shell. The testfixture.exe program runs scripts in the
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test/ folder to validate the core SQLite code. The testfixture program
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(and some other test programs too) is built and run when you type
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"make test".
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There are many other source files. Each has a succinct header comment that
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describes its purpose and role within the larger system.
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<a name="vauth"></a>
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## Verifying Code Authenticity
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The `manifest` file at the root directory of the source tree
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contains either a SHA3-256 hash or a SHA1 hash
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for every source file in the repository.
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The name of the version of the entire source tree is just the
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SHA3-256 hash of the `manifest` file itself, possibly with the
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last line of that file omitted if the last line begins with
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"`# Remove this line`".
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The `manifest.uuid` file should contain the SHA3-256 hash of the
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`manifest` file. If all of the above hash comparisons are correct, then
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you can be confident that your source tree is authentic and unadulterated.
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Details on the format for the `manifest` files are available
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[on the Fossil website](https://fossil-scm.org/fossil/doc/trunk/www/fileformat.wiki#manifest).
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The process of checking source code authenticity is automated by the
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makefile:
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> make verify-source
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Or on windows:
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> nmake /f Makefile.msc verify-source
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Using the makefile to verify source integrity is good for detecting
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accidental changes to the source tree, but malicious changes could be
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hidden by also modifying the makefiles.
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## Contacts
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The main SQLite website is [https://sqlite.org/](https://sqlite.org/)
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with geographically distributed backups at
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[https://www2.sqlite.org/](https://www2.sqlite.org) and
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[https://www3.sqlite.org/](https://www3.sqlite.org).
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