function.pg-lo-seek.html
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html> <head> <title>Seeks position within a large object</title> <meta http-equiv="content-type" content="text/html; charset=UTF-8"> </head> <body><div style="text-align: center;"> <div class="prev" style="text-align: left; float: left;"><a href="function.pg-lo-read.html">pg_lo_read</a></div> <div class="next" style="text-align: right; float: right;"><a href="function.pg-lo-tell.html">pg_lo_tell</a></div> <div class="up"><a href="ref.pgsql.html">PostgreSQL Functions</a></div> <div class="home"><a href="index.html">PHP Manual</a></div></div><hr /><div id="function.pg-lo-seek" class="refentry"> <div class="refnamediv"> <h1 class="refname">pg_lo_seek</h1> <p class="verinfo">(PHP 4 >= 4.2.0, PHP 5)</p><p class="refpurpose"><span class="refname">pg_lo_seek</span> — <span class="dc-title"> Seeks position within a large object </span></p> </div> <div class="refsect1 description"> <h3 class="title">Description</h3> <div class="methodsynopsis dc-description"> <span class="type">bool</span> <span class="methodname"><b><b>pg_lo_seek</b></b></span> ( <span class="methodparam"><span class="type">resource</span> <tt class="parameter">$large_object</tt></span> , <span class="methodparam"><span class="type">int</span> <tt class="parameter">$offset</tt></span> [, <span class="methodparam"><span class="type">int</span> <tt class="parameter">$whence</tt></span> ] )</div> <p class="para rdfs-comment"> <b>pg_lo_seek()</b> seeks a position within a large object resource. </p> <p class="para"> To use the large object interface, it is necessary to enclose it within a transaction block. </p> </div> <div class="refsect1 parameters"> <h3 class="title">Parameters</h3> <p class="para"> <dl> <dt> <span class="term"><i><tt class="parameter">large_object</tt></i></span> <dd> <p class="para"> PostgreSQL large object (LOB) resource, returned by <a href="function.pg-lo-open.html" class="function">pg_lo_open()</a>. </p> </dd> </dt> <dt> <span class="term"><i><tt class="parameter">offset</tt></i></span> <dd> <p class="para"> The number of bytes to seek. </p> </dd> </dt> <dt> <span class="term"><i><tt class="parameter">whence</tt></i></span> <dd> <p class="para"> One of the constants <b><tt>PGSQL_SEEK_SET</tt></b> (seek from object start), <b><tt>PGSQL_SEEK_CUR</tt></b> (seek from current position) or <b><tt>PGSQL_SEEK_END</tt></b> (seek from object end) . </p> </dd> </dt> </dl> </p> </div> <div class="refsect1 returnvalues"> <h3 class="title">Return Values</h3> <p class="para"> Returns <b><tt>TRUE</tt></b> on success or <b><tt>FALSE</tt></b> on failure. </p> </div> <div class="refsect1 examples"> <h3 class="title">Examples</h3> <p class="para"> <div class="example"> <p><b>Example #1 <b>pg_lo_seek()</b> example</b></p> <div class="example-contents"><div class="phpcode"><code><span style="color: #000000"><span style="color: #0000BB"><?php<br /> $doc_oid </span><span style="color: #007700">= </span><span style="color: #0000BB">189762345</span><span style="color: #007700">;<br /> </span><span style="color: #0000BB">$database </span><span style="color: #007700">= </span><span style="color: #0000BB">pg_connect</span><span style="color: #007700">(</span><span style="color: #DD0000">"dbname=jacarta"</span><span style="color: #007700">);<br /> </span><span style="color: #0000BB">pg_query</span><span style="color: #007700">(</span><span style="color: #0000BB">$database</span><span style="color: #007700">, </span><span style="color: #DD0000">"begin"</span><span style="color: #007700">);<br /> </span><span style="color: #0000BB">$handle </span><span style="color: #007700">= </span><span style="color: #0000BB">pg_lo_open</span><span style="color: #007700">(</span><span style="color: #0000BB">$database</span><span style="color: #007700">, </span><span style="color: #0000BB">$doc_oid</span><span style="color: #007700">, </span><span style="color: #DD0000">"r"</span><span style="color: #007700">);<br /> </span><span style="color: #FF8000">// Skip first 50000 bytes<br /> </span><span style="color: #0000BB">pg_lo_seek</span><span style="color: #007700">(</span><span style="color: #0000BB">$handle</span><span style="color: #007700">, </span><span style="color: #0000BB">50000</span><span style="color: #007700">, </span><span style="color: #0000BB">PGSQL_SEEK_SET</span><span style="color: #007700">);<br /> </span><span style="color: #FF8000">// Read the next 10000 bytes<br /> </span><span style="color: #0000BB">$data </span><span style="color: #007700">= </span><span style="color: #0000BB">pg_lo_read</span><span style="color: #007700">(</span><span style="color: #0000BB">$handle</span><span style="color: #007700">, </span><span style="color: #0000BB">10000</span><span style="color: #007700">);<br /> </span><span style="color: #0000BB">pg_query</span><span style="color: #007700">(</span><span style="color: #0000BB">$database</span><span style="color: #007700">, </span><span style="color: #DD0000">"commit"</span><span style="color: #007700">);<br /> echo </span><span style="color: #0000BB">$data</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">?></span></span></code></div> </div> </div> </p> </div> <div class="refsect1 seealso"> <h3 class="title">See Also</h3> <p class="para"> <ul class="simplelist"> <li class="member"><a href="function.pg-lo-tell.html" class="function" rel="rdfs-seeAlso">pg_lo_tell()</a></li> </ul> </p> </div></div><hr /><div style="text-align: center;"> <div class="prev" style="text-align: left; float: left;"><a href="function.pg-lo-read.html">pg_lo_read</a></div> <div class="next" style="text-align: right; float: right;"><a href="function.pg-lo-tell.html">pg_lo_tell</a></div> <div class="up"><a href="ref.pgsql.html">PostgreSQL Functions</a></div> <div class="home"><a href="index.html">PHP Manual</a></div></div></body></html>⌨️ 快捷键说明
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