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C Is Best</a></div> +<div class="fancy-toc2"><a href="#performance">1.1. Performance</a></div> +<div class="fancy-toc2"><a href="#compatibility">1.2. Compatibility</a></div> +<div class="fancy-toc2"><a href="#low_dependency">1.3. Low-Dependency</a></div> +<div class="fancy-toc2"><a href="#stability">1.4. Stability</a></div> +<div class="fancy-toc1"><a href="#why_isn_t_sqlite_coded_in_an_object_oriented_language_">2. Why Isn't SQLite Coded In An Object-Oriented Language?</a></div> +<div class="fancy-toc1"><a href="#why_isn_t_sqlite_coded_in_a_safe_language_">3. Why Isn't SQLite Coded In A "Safe" Language?</a></div> +</div> +</div> +<script> +function toggle_toc(){ +var sub = document.getElementById("toc_sub") +var mk = document.getElementById("toc_mk") +if( sub.style.display!="block" ){ +sub.style.display = "block"; +mk.innerHTML = "▼"; +} else { +sub.style.display = "none"; +mk.innerHTML = "►"; +} +} +</script> +</div> + + + + +<h1 id="c_is_best"><span>1. </span>C Is Best</h1> + +<blockquote><table border="1"><tr><td> +Note: Sections 2.0 and 3.0 of this article were added in response +to comments on +<a href="https://news.ycombinator.com/item?id=16585120">Hacker News</a> and +<a href="https://www.reddit.com/r/programming/comments/84fzoc/why_is_sqlite_coded_in_c/">Reddit</a>. +</td></tr></table></blockquote> + +<p> +Since its inception on 2000-05-29, SQLite has been implemented in generic C. +C was and continues to be the best language for implementing a software +library like SQLite. There are no plans to recode SQLite in any other +programming language at this time. + +</p><p> +The reasons why C is the best language to implement SQLite include: + + +</p><ul> +<li> Performance +</li><li> Compatibility +</li><li> Low-dependency +</li><li> Stability +</li></ul> + +<h2 id="performance"><span>1.1. </span>Performance</h2> + +<p>An intensively used low-level library like SQLite needs to be fast. +(And SQLite is fast, see <a href="intern-v-extern-blob.html">Internal Versus External BLOBs</a> and +<a href="fasterthanfs.html">35% Faster Than The Filesystem</a> for example.) + +</p><p>C is a great language for writing fast code. C is sometimes +described as "portable assembly language". It enables to developers +to code as close to the underlying hardware as possible while still +remaining portable across platforms. + +</p><p>Other programming languages sometimes claim to be "as fast as C". +But no other language claims to be faster than C for general-purpose +programming, because none are. + +</p><h2 id="compatibility"><span>1.2. </span>Compatibility</h2> + +<p>Nearly all systems have the ability to call libraries +written in C. This is not true of other implementation languages. + +</p><p>So, for example, Android applications written in Java are able to +invoke SQLite (through an adaptor). Maybe it would have been more +convenient for Android if SQLite had been coded in Java as that would +make the interface simpler. However, on iPhone applications are coded +in Objective-C or Swift, neither of which have the ability to call +libraries written in Java. Thus, SQLite would be unusable on iPhones +had it been written in Java. + +</p><h2 id="low_dependency"><span>1.3. </span>Low-Dependency</h2> + +<p>Libraries written in C do not have a huge run-time dependency. +In its minimum configuration, SQLite requires only the following +routines from the standard C library: + +</p><center> +<table border="0"> +<tr> +<td valign="top"> +<ul> +<li> memcmp() +</li><li> memcpy() +</li><li> memmove() +</li><li> memset() +</li></ul> +</td> +<td> </td> +<td valign="top"> +<ul> +<li> strcmp() +</li><li> strlen() +</li><li> strncmp() +</li></ul> +</td> +</tr> +</table> +</center> + +<p> +In a more complete build, SQLite also uses library routines like +malloc() and free() and operating system interfaces for opening, reading, +writing, and closing files. But even then, the number of dependencies +is very small. Other "modern" language, in contrast, often require +multi-megabyte runtimes loaded with thousands and thousands of interfaces. + +</p><h2 id="stability"><span>1.4. </span>Stability</h2> + +<p> +The C language is old and boring. +It is a well-known and well-understood language. +This is exactly what one wants when developing a module like SQLite. +Writing a small, fast, and reliable database engine is hard enough as it +is without the implementation language changing out from under you with +each update to the implementation language specification. + +</p><h1 id="why_isn_t_sqlite_coded_in_an_object_oriented_language_"><span>2. </span>Why Isn't SQLite Coded In An Object-Oriented Language?</h1> + +<p> +Some programmers cannot imagine developing a complex system like +SQLite in a language that is not "object oriented". So why is +SQLite not coded in C++ or Java? + +</p><ol> +<li><p> +Libraries written in C++ or Java can generally only be used by +applications written in the same language. It is difficult to +get an application written in Haskell or Java to invoke a library +written in C++. On the other hand, libraries written in C are +callable from any programming language. + +</p></li><li><p> +Object-Oriented is a design pattern, not a programming language. +You can do object-oriented programming in any language you want, +including assembly language. Some languages (ex: C++ or Java) make +object-oriented easier. But you can still do object-oriented programming +in languages like C. + +</p></li><li><p> +Object-oriented is not the only valid design pattern. +Many programmers have been taught to think purely in terms of +objects. And, to be fair, objects are often a good way to +decompose a problem. But objects are not the only way, and are +not always the best way to decompose a problem. Sometimes good old +procedural code is easier to write, easier to maintain and understand, +and faster than object-oriented code. + +</p></li><li><p> +When SQLite was first being developed, Java was a young and immature +language. C++ was older, but was undergoing such growing pains that +it was difficult to find any two C++ compilers that worked the same +way. So C was definitely a better choice back when SQLite was first +being developed. The situation is less stark now, but there is little +to no benefit in recoding SQLite at this point. +</p></li></ol> + +<h1 id="why_isn_t_sqlite_coded_in_a_safe_language_"><span>3. </span>Why Isn't SQLite Coded In A "Safe" Language?</h1> + +<p> +There has lately been a lot of interest in "safe" programming languages +like Rust or Go in which it is impossible, or is at least difficult, to make +common programming errors like memory leaks or array overruns. So the +question often arises as to why SQLite is not coded in a "safe" language. + +</p><ol> +<li><p> +None of the safe programming languages existed for the first 10 years +of SQLite's existence. SQLite could be recoded in Go or Rust, but doing +so would probably introduce far more bugs than would be fixed, and it +seems also likely to result in slower code. + +</p></li><li><p> +Safe languages insert additional machine branches to do things like +verify that array accesses are in-bounds. In correct code, those +branches are never taken. That means that the machine code cannot +be 100% branch tested, which is an important component of SQLite's +quality strategy. + +</p></li><li><p> +Safe languages usually want to abort if they encounter an out-of-memory +(OOM) situation. SQLite is designed to recover gracefully from an OOM. +It is unclear how this could be accomplished in the current crop of +safe languages. + +</p></li><li><p> +All of the existing safe languages are new. The developers of SQLite +applaud the efforts of computer language researchers in trying to +develop languages that are easier to program safely. We encourage these +efforts to continue. But we ourselves are more interested in old and +boring languages when it comes to implementing SQLite. +</p></li></ol> + +<p> +All that said, it is possible that SQLite might +one day be recoded in Rust. Recoding SQLite in Go is unlikely +since Go hates assert(). But Rust is a possibility. Some +preconditions that must occur before SQLite is recoded in Rust +include: + +</p><p> +</p><ol type="A"> +<li> Rust needs to mature a little more, stop changing so fast, and + move further toward being old and boring. +</li><li> Rust needs to demonstrate that it can be used to create general-purpose + libraries that are callable from all other programming languages. +</li><li> Rust needs to demonstrate that it can produce object code that + works on obscure embedded devices, including devices that lack + an operating system. +</li><li> Rust needs to pick up the necessary tooling that enables one to + do 100% branch coverage testing of the compiled binaries. +</li><li> Rust needs a mechanism to recover gracefully from OOM errors. +</li><li> Rust needs to demonstrate that it can do the kinds of work that + C does in SQLite without a significant speed penalty. +</li></ol> + +<p> +If you are a "rustacean" and feel that Rust already meets the +preconditions listed above, and that SQLite should be recoded in +Rust, then you are welcomed and encouraged +to contact the SQLite developers privately +and argue your case. +</p><p align="center"><small><i>This page last modified on <a href="https://sqlite.org/docsrc/honeypot" id="mtimelink" data-href="https://sqlite.org/docsrc/finfo/pages/whyc.in?m=a3c9b502ed9d12ab7">2022-07-29 00:41:26</a> UTC </small></i></p> + |