diff options
Diffstat (limited to '')
| -rw-r--r-- | www/session/sqlite3session_changeset.html | 228 |
1 files changed, 228 insertions, 0 deletions
diff --git a/www/session/sqlite3session_changeset.html b/www/session/sqlite3session_changeset.html new file mode 100644 index 0000000..df9a39c --- /dev/null +++ b/www/session/sqlite3session_changeset.html @@ -0,0 +1,228 @@ +<!DOCTYPE html> +<html><head> +<meta name="viewport" content="width=device-width, initial-scale=1.0"> +<meta http-equiv="content-type" content="text/html; charset=UTF-8"> +<link href="../sqlite.css" rel="stylesheet"> +<title>Generate A Changeset From A Session Object</title> +<!-- path=../ --> +</head> +<body> +<div class=nosearch> +<a href="../index.html"> +<img class="logo" src="../images/sqlite370_banner.gif" alt="SQLite" border="0"> +</a> +<div><!-- IE hack to prevent disappearing logo --></div> +<div class="tagline desktoponly"> +Small. Fast. Reliable.<br>Choose any three. +</div> +<div class="menu mainmenu"> +<ul> +<li><a href="../index.html">Home</a> +<li class='mobileonly'><a href="javascript:void(0)" onclick='toggle_div("submenu")'>Menu</a> +<li class='wideonly'><a href='../about.html'>About</a> +<li class='desktoponly'><a href="../docs.html">Documentation</a> +<li class='desktoponly'><a href="../download.html">Download</a> +<li class='wideonly'><a href='../copyright.html'>License</a> +<li class='desktoponly'><a href="../support.html">Support</a> +<li class='desktoponly'><a href="../prosupport.html">Purchase</a> +<li class='search' id='search_menubutton'> +<a href="javascript:void(0)" onclick='toggle_search()'>Search</a> +</ul> +</div> +<div class="menu submenu" id="submenu"> +<ul> +<li><a href='../about.html'>About</a> +<li><a href='../docs.html'>Documentation</a> +<li><a href='../download.html'>Download</a> +<li><a href='../support.html'>Support</a> +<li><a href='../prosupport.html'>Purchase</a> +</ul> +</div> +<div class="searchmenu" id="searchmenu"> +<form method="GET" action="../search"> +<select name="s" id="searchtype"> +<option value="d">Search Documentation</option> +<option value="c">Search Changelog</option> +</select> +<input type="text" name="q" id="searchbox" value=""> +<input type="submit" value="Go"> +</form> +</div> +</div> +<script> +function toggle_div(nm) { +var w = document.getElementById(nm); +if( w.style.display=="block" ){ +w.style.display = "none"; +}else{ +w.style.display = "block"; +} +} +function toggle_search() { +var w = document.getElementById("searchmenu"); +if( w.style.display=="block" ){ +w.style.display = "none"; +} else { +w.style.display = "block"; +setTimeout(function(){ +document.getElementById("searchbox").focus() +}, 30); +} +} +function div_off(nm){document.getElementById(nm).style.display="none";} +window.onbeforeunload = function(e){div_off("submenu");} +/* Disable the Search feature if we are not operating from CGI, since */ +/* Search is accomplished using CGI and will not work without it. */ +if( !location.origin || !location.origin.match || !location.origin.match(/http/) ){ +document.getElementById("search_menubutton").style.display = "none"; +} +/* Used by the Hide/Show button beside syntax diagrams, to toggle the */ +function hideorshow(btn,obj){ +var x = document.getElementById(obj); +var b = document.getElementById(btn); +if( x.style.display!='none' ){ +x.style.display = 'none'; +b.innerHTML='show'; +}else{ +x.style.display = ''; +b.innerHTML='hide'; +} +return false; +} +var antiRobot = 0; +function antiRobotGo(){ +if( antiRobot!=3 ) return; +antiRobot = 7; +var j = document.getElementById("mtimelink"); +if(j && j.hasAttribute("data-href")) j.href=j.getAttribute("data-href"); +} +function antiRobotDefense(){ +document.body.onmousedown=function(){ +antiRobot |= 2; +antiRobotGo(); +document.body.onmousedown=null; +} +document.body.onmousemove=function(){ +antiRobot |= 2; +antiRobotGo(); +document.body.onmousemove=null; +} +setTimeout(function(){ +antiRobot |= 1; +antiRobotGo(); +}, 100) +antiRobotGo(); +} +antiRobotDefense(); +</script> +<a href="../session/intro.html"><h2>Session Module C Interface</h2></a><h2>Generate A Changeset From A Session Object</h2><blockquote><pre>int sqlite3session_changeset( + sqlite3_session *pSession, /* Session object */ + int *pnChangeset, /* OUT: Size of buffer at *ppChangeset */ + void **ppChangeset /* OUT: Buffer containing changeset */ +); +</pre></blockquote><p> +Obtain a changeset containing changes to the tables attached to the +session object passed as the first argument. If successful, +set *ppChangeset to point to a buffer containing the changeset +and *pnChangeset to the size of the changeset in bytes before returning +SQLITE_OK. If an error occurs, set both *ppChangeset and *pnChangeset to +zero and return an SQLite error code.</p> + +<p>A changeset consists of zero or more INSERT, UPDATE and/or DELETE changes, +each representing a change to a single row of an attached table. An INSERT +change contains the values of each field of a new database row. A DELETE +contains the original values of each field of a deleted database row. An +UPDATE change contains the original values of each field of an updated +database row along with the updated values for each updated non-primary-key +column. It is not possible for an UPDATE change to represent a change that +modifies the values of primary key columns. If such a change is made, it +is represented in a changeset as a DELETE followed by an INSERT.</p> + +<p>Changes are not recorded for rows that have NULL values stored in one or +more of their PRIMARY KEY columns. If such a row is inserted or deleted, +no corresponding change is present in the changesets returned by this +function. If an existing row with one or more NULL values stored in +PRIMARY KEY columns is updated so that all PRIMARY KEY columns are non-NULL, +only an INSERT is appears in the changeset. Similarly, if an existing row +with non-NULL PRIMARY KEY values is updated so that one or more of its +PRIMARY KEY columns are set to NULL, the resulting changeset contains a +DELETE change only.</p> + +<p>The contents of a changeset may be traversed using an iterator created +using the <a href="../session/sqlite3changeset_start.html">sqlite3changeset_start()</a> API. A changeset may be applied to +a database with a compatible schema using the <a href="../session/sqlite3changeset_apply.html">sqlite3changeset_apply()</a> +API.</p> + +<p>Within a changeset generated by this function, all changes related to a +single table are grouped together. In other words, when iterating through +a changeset or when applying a changeset to a database, all changes related +to a single table are processed before moving on to the next table. Tables +are sorted in the same order in which they were attached (or auto-attached) +to the sqlite3_session object. The order in which the changes related to +a single table are stored is undefined.</p> + +<p>Following a successful call to this function, it is the responsibility of +the caller to eventually free the buffer that *ppChangeset points to using +<a href="../c3ref/free.html">sqlite3_free()</a>.</p> + +<p><h3>Changeset Generation</h3></p> + +<p>Once a table has been attached to a session object, the session object +records the primary key values of all new rows inserted into the table. +It also records the original primary key and other column values of any +deleted or updated rows. For each unique primary key value, data is only +recorded once - the first time a row with said primary key is inserted, +updated or deleted in the lifetime of the session.</p> + +<p>There is one exception to the previous paragraph: when a row is inserted, +updated or deleted, if one or more of its primary key columns contain a +NULL value, no record of the change is made.</p> + +<p>The session object therefore accumulates two types of records - those +that consist of primary key values only (created when the user inserts +a new record) and those that consist of the primary key values and the +original values of other table columns (created when the users deletes +or updates a record).</p> + +<p>When this function is called, the requested changeset is created using +both the accumulated records and the current contents of the database +file. Specifically:</p> + +<p><ul> + <li> For each record generated by an insert, the database is queried + for a row with a matching primary key. If one is found, an INSERT + change is added to the changeset. If no such row is found, no change + is added to the changeset.</p> + +<p> <li> For each record generated by an update or delete, the database is + queried for a row with a matching primary key. If such a row is + found and one or more of the non-primary key fields have been + modified from their original values, an UPDATE change is added to + the changeset. Or, if no such row is found in the table, a DELETE + change is added to the changeset. If there is a row with a matching + primary key in the database, but all fields contain their original + values, no change is added to the changeset. +</ul></p> + +<p>This means, amongst other things, that if a row is inserted and then later +deleted while a session object is active, neither the insert nor the delete +will be present in the changeset. Or if a row is deleted and then later a +row with the same primary key values inserted while a session object is +active, the resulting changeset will contain an UPDATE change instead of +a DELETE and an INSERT.</p> + +<p>When a session object is disabled (see the <a href="../session/sqlite3session_enable.html">sqlite3session_enable()</a> API), +it does not accumulate records when rows are inserted, updated or deleted. +This may appear to have some counter-intuitive effects if a single row +is written to more than once during a session. For example, if a row +is inserted while a session object is enabled, then later deleted while +the same session object is disabled, no INSERT record will appear in the +changeset, even though the delete took place while the session was disabled. +Or, if one field of a row is updated while a session is disabled, and +another field of the same row is updated while the session is enabled, the +resulting changeset will contain an UPDATE change that updates both fields. +</p><p>See also lists of + <a href="../session/objlist.html">Objects</a>, + <a href="../session/constlist.html">Constants</a>, and + <a href="../session/funclist.html">Functions</a>.</p> + |