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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"><html><head><title>Assumptions</title><style type="text/css">body {    margin: auto;    font-family: "Verdana" "sans-serif";    padding: 8px 1%;}a { color: #45735f }a:visited { color: #734559 }.logo { position:absolute; margin:3px; }.tagline {  float:right;  text-align:right;  font-style:italic;  width:240px;  margin:12px;  margin-top:58px;}.toolbar {  font-variant: small-caps;  text-align: center;  line-height: 1.6em;  margin: 0;  padding:1px 8px;}.toolbar a { color: white; text-decoration: none; padding: 6px 12px; }.toolbar a:visited { color: white; }.toolbar a:hover { color: #80a796; background: white; }.content    { margin: 5%; }.content dt { font-weight:bold; }.content dd { margin-bottom: 25px; margin-left:20%; }.content ul { padding:0px; padding-left: 15px; margin:0px; }/* rounded corners */.se  { background: url(images/se.png) 100% 100% no-repeat #80a796}.sw  { background: url(images/sw.png) 0% 100% no-repeat }.ne  { background: url(images/ne.png) 100% 0% no-repeat }.nw  { background: url(images/nw.png) 0% 0% no-repeat }</style><meta http-equiv="content-type" content="text/html; charset=UTF-8">  </head><body><div><!-- container div to satisfy validator --><a href="index.html"><img class="logo" src="images/SQLite.gif" alt="SQLite Logo" border="0"></a><div><!-- IE hack to prevent disappearing logo--></div><div class="tagline">Small. Fast. Reliable.<br>Choose any three.</div><table width=100% style="clear:both"><tr><td>  <div class="se"><div class="sw"><div class="ne"><div class="nw">  <div class="toolbar">    <a href="about.html">About</a>    <a href="sitemap.html">Sitemap</a>    <a href="docs.html">Documentation</a>    <a href="download.html">Download</a>    <a href="copyright.html">License</a>    <a href="news.html">News</a>    <a href="http://www.sqlite.org/cvstrac/index">Developers</a>    <a href="support.html">Support</a>  </div></div></div></div></div></td></tr></table>  <h2>Assumptions Made By SQLite</h2><p>This document defines behavior that SQLite expects from the applicationthat is using SQLite.  We call these "assumptions", but they might also becalled "Application Requirements" since they can be thought of additionalrequirements that are imposed on any application that uses SQLite.</p><p>Another way of looking at these invariants is that they are limitationsor constraints on the use of SQLite.  If an application fails to abide bythe assumptions described here, then the behavior of SQLite will beundefined and probably undesirable.</p><p>Yet another way of thinking about these invariants is that all of thestatements listed below must be true in order for SQLite to operate correctly.</p><table cellspacing="20"><tr><td valign="top">A10512</td><td valign="top">The input to <a href="c3ref/complete.html">sqlite3_complete()</a> must be a zero-terminatedUTF-8 string. </td></tr><tr><td valign="top">A10513</td><td valign="top">The input to <a href="c3ref/complete.html">sqlite3_complete16()</a> must be a zero-terminatedUTF-16 string in native byte order. </td></tr><tr><td valign="top">A12016</td><td valign="top">The C parameter to <a href="c3ref/close.html">sqlite3_close(C)</a> must be either a NULLpointer or an <a href="c3ref/sqlite3.html">sqlite3</a> object pointer obtainedfrom <a href="c3ref/open.html">sqlite3_open()</a>, <a href="c3ref/open.html">sqlite3_open16()</a>, or<a href="c3ref/open.html">sqlite3_open_v2()</a>, and not previously closed. </td></tr><tr><td valign="top">A12141</td><td valign="top">The first parameter to <a href="c3ref/exec.html">sqlite3_exec()</a> must be an valid and open<a href="c3ref/sqlite3.html">database connection</a>. </td></tr><tr><td valign="top">A12142</td><td valign="top">The database connection must not be closed while<a href="c3ref/exec.html">sqlite3_exec()</a> is running. </td></tr><tr><td valign="top">A12143</td><td valign="top">The calling function should use <a href="c3ref/free.html">sqlite3_free()</a> to freethe memory that *errmsg is left pointing at once the errormessage is no longer needed. </td></tr><tr><td valign="top">A12145</td><td valign="top">The SQL statement text in the 2nd parameter to <a href="c3ref/exec.html">sqlite3_exec()</a>must remain unchanged while <a href="c3ref/exec.html">sqlite3_exec()</a> is running. </td></tr><tr><td valign="top">A12232</td><td valign="top">If a separate thread performs a new <a href="lang_insert.html">INSERT</a> on the samedatabase connection while the <a href="c3ref/last_insert_rowid.html">sqlite3_last_insert_rowid()</a>function is running and thus changes the last insert rowid,then the value returned by <a href="c3ref/last_insert_rowid.html">sqlite3_last_insert_rowid()</a> isunpredictable and might not equal either the old or the newlast insert rowid. </td></tr><tr><td valign="top">A12252</td><td valign="top">If a separate thread makes changes on the same database connectionwhile <a href="c3ref/changes.html">sqlite3_changes()</a> is running then the value returnedis unpredictable and not meaningful. </td></tr><tr><td valign="top">A12264</td><td valign="top">If a separate thread makes changes on the same database connectionwhile <a href="c3ref/total_changes.html">sqlite3_total_changes()</a> is running then the valuereturned is unpredictable and not meaningful. </td></tr><tr><td valign="top">A12279</td><td valign="top">If the database connection closes while <a href="c3ref/interrupt.html">sqlite3_interrupt()</a>is running then bad things will likely happen. </td></tr><tr><td valign="top">A12319</td><td valign="top">A busy handler must not close the database connectionor <a href="c3ref/stmt.html">prepared statement</a> that invoked the busy handler. </td></tr><tr><td valign="top">A12936</td><td valign="top">If another thread changes the autocommit status of the databaseconnection while this routine is running, then the return valueis undefined. </td></tr><tr><td valign="top">A13154</td><td valign="top">The <a href="c3ref/sqlite3.html">database connection</a> pointer D in a call to<a href="c3ref/next_stmt.html">sqlite3_next_stmt(D,S)</a> must refer to an open databaseconnection and in particular must not be a NULL pointer. </td></tr><tr><td valign="top">A13751</td><td valign="top">If two or more threads call one or more<a href="c3ref/column_database_name.html">column metadata interfaces</a>for the same <a href="c3ref/stmt.html">prepared statement</a> and result columnat the same time then the results are undefined. </td></tr><tr><td valign="top">A17350</td><td valign="top">The pointer arguments to <a href="c3ref/free.html">sqlite3_free()</a> and <a href="c3ref/free.html">sqlite3_realloc()</a>must be either NULL or else pointers obtained from a priorinvocation of <a href="c3ref/free.html">sqlite3_malloc()</a> or <a href="c3ref/free.html">sqlite3_realloc()</a> that havenot yet been released. </td></tr><tr><td valign="top">A17351</td><td valign="top">The application must not read or write any part ofa block of memory after it has been released using<a href="c3ref/free.html">sqlite3_free()</a> or <a href="c3ref/free.html">sqlite3_realloc()</a>. </td></tr><tr><td valign="top">A21001</td><td valign="top">      If a system failure occurs during or after a "create file"      operation, but before the created file has been <i>synced</i>, then       SQLite assumes that it is possible that the created file may not      exist following system recovery.</td></tr><tr><td valign="top">A21002</td><td valign="top">      If a "create file" operation is executed by SQLite, and then the      created file <i>synced</i>, then SQLite assumes that the file-system      modifications corresponding to the "create file" operation have been      committed to persistent media. It is assumed that if a system      failure occurs any time after the file has been successfully       <i>synced</i>, then the file is guaranteed to appear in the file-system      following system recovery.</td></tr><tr><td valign="top">A21003</td><td valign="top">      If a system failure occurs at any time after a "delete file"       operation (call to the VFS xDelete() method) returns successfully, it is      assumed that the file-system will not contain the deleted file following      system recovery.</td></tr><tr><td valign="top">A21004</td><td valign="top">      If a system failure occurs during a "delete file" operation,      it is assumed that following system recovery the file-system will       either contain the file being deleted in the state it was in before      the operation was attempted, or not contain the file at all. It is       assumed that it is not possible for the file to have become corrupted      purely as a result of a failure occuring during a "delete file"       operation.</td></tr><tr><td valign="top">A21005</td><td valign="top">      If a system failure occurs during or after a "truncate file"      operation, but before the truncated file has been <i>synced</i>, then       SQLite assumes that the size of the truncated file is either as large      or larger than the size that it was to be truncated to.</td></tr><tr><td valign="top">A21006</td><td valign="top">      If a system failure occurs during or after a "truncate file"      operation, but before the truncated file has been <i>synced</i>, then       it is assumed that the contents of the file up to the size that the      file was to be truncated to are not corrupted.</td></tr><tr><td valign="top">A21007</td><td valign="top">      If a "truncate file" operation is executed by SQLite, and then the      truncated file <i>synced</i>, then SQLite assumes that the file-system      modifications corresponding to the "truncate file" operation have been      committed to persistent media. It is assumed that if a system      failure occurs any time after the file has been successfully       <i>synced</i>, then the effects of the file truncation are guaranteed      to appear in the file system following recovery.</td></tr><tr><td valign="top">A21008</td><td valign="top">      If a system failure occurs during or after a "write file"      operation, but before the corresponding file has been <i>synced</i>,       then it is assumed that the content of all sectors spanned by the      <i>write file</i> operation are untrustworthy following system       recovery. This includes regions of the sectors that were not      actually modified by the write file operation.</td></tr><tr><td valign="top">A21009</td><td valign="top">      If a system failure occurs during or after a "write file"      operation that causes the file to grow, but before the corresponding       file has been <i>synced</i>, then it is assumed that the size of       the file following recovery is as large or larger than it was when      it was most recently <i>synced</i>.</td></tr><tr><td valign="top">A21010</td><td valign="top">      It is assumed that writing a series of sequential blocks of data to       a file in order is faster than writing the same blocks in an arbitrary      order.</td></tr><tr><td valign="top">A21011</td><td valign="top">      If a system failure occurs on a system that supports the       <i>atomic-write</i> property for blocks of size <i>N</i> bytes      following an aligned write of <i>N</i>       bytes to a file but before the file has been succesfully <i>synced</i>,      then is is assumed following recovery that all sectors spanned by the      write operation were correctly updated, or that none of the sectors were      modified at all.</td></tr><tr><td valign="top">A21012</td><td valign="top">      If a system failure occurs on a system that supports the       <i>safe-append</i> following a write operation that appends data      to the end of the file without modifying any of the existing file       content but before the file has been succesfully <i>synced</i>,      then is is assumed following recovery that either the data was      correctly appended to the file, or that the file size remains       unchanged. It is assumed that it is impossible that the file be      extended but populated with incorrect data.</td></tr><tr><td valign="top">A21013</td><td valign="top">      Following a system recovery, if a device sector is deemed to be      untrustworthy as defined by A21008 and neither A21011 or A21012       apply to the range of bytes written, then no assumption can be      made about the content of the sector following recovery. It is      assumed that it is possible for such a sector to be written       correctly, not written at all, populated with garbage data or any      combination thereof.</td></tr><tr><td valign="top">A21014</td><td valign="top">      If a system failure occurs on a system that supports the      <i>sequential-write</i> property, then it is assumed that all       operations completed before the last time any file was <i>synced</i>       have been successfully committed to persistent media.</td></tr><tr><td valign="top">A21015</td><td valign="top">      If a system failure occurs on a system that supports the      <i>sequential-write</i> property, then it is assumed that the set      of possible states that the file-system may be in following recovery      is the same as if each of the write operations performed since the most      recent time a file was <i>synced</i> was itself followed by a <i>sync      file</i> operation, and that the system failure may have occured during      any of the write or <i>sync file</i> operations.</td></tr></table><hr><small><i>This page last modified 2008/07/22 17:19:32 UTC</i></small></div></body></html>
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