diff options
Diffstat (limited to 'doc/src/sgml/html/ecpg-lo.html')
| -rw-r--r-- | doc/src/sgml/html/ecpg-lo.html | 100 |
1 files changed, 100 insertions, 0 deletions
diff --git a/doc/src/sgml/html/ecpg-lo.html b/doc/src/sgml/html/ecpg-lo.html new file mode 100644 index 0000000..535e4ad --- /dev/null +++ b/doc/src/sgml/html/ecpg-lo.html @@ -0,0 +1,100 @@ +<?xml version="1.0" encoding="UTF-8" standalone="no"?> +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>36.12. Large Objects</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="ecpg-library.html" title="36.11. Library Functions" /><link rel="next" href="ecpg-cpp.html" title="36.13. C++ Applications" /></head><body id="docContent" class="container-fluid col-10"><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">36.12. Large Objects</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="ecpg-library.html" title="36.11. Library Functions">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="ecpg.html" title="Chapter 36. ECPG — Embedded SQL in C">Up</a></td><th width="60%" align="center">Chapter 36. <span xmlns="http://www.w3.org/1999/xhtml" class="application">ECPG</span> — Embedded <acronym xmlns="http://www.w3.org/1999/xhtml" class="acronym">SQL</acronym> in C</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 14.5 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="ecpg-cpp.html" title="36.13. C++ Applications">Next</a></td></tr></table><hr></hr></div><div class="sect1" id="ECPG-LO"><div class="titlepage"><div><div><h2 class="title" style="clear: both">36.12. Large Objects</h2></div></div></div><p> + Large objects are not directly supported by ECPG, but ECPG + application can manipulate large objects through the libpq large + object functions, obtaining the necessary <code class="type">PGconn</code> + object by calling the <code class="function">ECPGget_PGconn()</code> + function. (However, use of + the <code class="function">ECPGget_PGconn()</code> function and touching + <code class="type">PGconn</code> objects directly should be done very carefully + and ideally not mixed with other ECPG database access calls.) + </p><p> + For more details about the <code class="function">ECPGget_PGconn()</code>, see + <a class="xref" href="ecpg-library.html" title="36.11. Library Functions">Section 36.11</a>. For information about the large + object function interface, see <a class="xref" href="largeobjects.html" title="Chapter 35. Large Objects">Chapter 35</a>. + </p><p> + Large object functions have to be called in a transaction block, so + when autocommit is off, <code class="command">BEGIN</code> commands have to + be issued explicitly. + </p><p> + <a class="xref" href="ecpg-lo.html#ECPG-LO-EXAMPLE" title="Example 36.2. ECPG Program Accessing Large Objects">Example 36.2</a> shows an example program that + illustrates how to create, write, and read a large object in an + ECPG application. + </p><div class="example" id="ECPG-LO-EXAMPLE"><p class="title"><strong>Example 36.2. ECPG Program Accessing Large Objects</strong></p><div class="example-contents"><pre class="programlisting"> +#include <stdio.h> +#include <stdlib.h> +#include <libpq-fe.h> +#include <libpq/libpq-fs.h> + +EXEC SQL WHENEVER SQLERROR STOP; + +int +main(void) +{ + PGconn *conn; + Oid loid; + int fd; + char buf[256]; + int buflen = 256; + char buf2[256]; + int rc; + + memset(buf, 1, buflen); + + EXEC SQL CONNECT TO testdb AS con1; + EXEC SQL SELECT pg_catalog.set_config('search_path', '', false); EXEC SQL COMMIT; + + conn = ECPGget_PGconn("con1"); + printf("conn = %p\n", conn); + + /* create */ + loid = lo_create(conn, 0); + if (loid &lt; 0) + printf("lo_create() failed: %s", PQerrorMessage(conn)); + + printf("loid = %d\n", loid); + + /* write test */ + fd = lo_open(conn, loid, INV_READ|INV_WRITE); + if (fd &lt; 0) + printf("lo_open() failed: %s", PQerrorMessage(conn)); + + printf("fd = %d\n", fd); + + rc = lo_write(conn, fd, buf, buflen); + if (rc &lt; 0) + printf("lo_write() failed\n"); + + rc = lo_close(conn, fd); + if (rc &lt; 0) + printf("lo_close() failed: %s", PQerrorMessage(conn)); + + /* read test */ + fd = lo_open(conn, loid, INV_READ); + if (fd &lt; 0) + printf("lo_open() failed: %s", PQerrorMessage(conn)); + + printf("fd = %d\n", fd); + + rc = lo_read(conn, fd, buf2, buflen); + if (rc &lt; 0) + printf("lo_read() failed\n"); + + rc = lo_close(conn, fd); + if (rc &lt; 0) + printf("lo_close() failed: %s", PQerrorMessage(conn)); + + /* check */ + rc = memcmp(buf, buf2, buflen); + printf("memcmp() = %d\n", rc); + + /* cleanup */ + rc = lo_unlink(conn, loid); + if (rc &lt; 0) + printf("lo_unlink() failed: %s", PQerrorMessage(conn)); + + EXEC SQL COMMIT; + EXEC SQL DISCONNECT ALL; + return 0; +} +</pre></div></div><br class="example-break" /></div><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navfooter"><hr></hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ecpg-library.html" title="36.11. Library Functions">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="ecpg.html" title="Chapter 36. ECPG — Embedded SQL in C">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="ecpg-cpp.html" title="36.13. C++ Applications">Next</a></td></tr><tr><td width="40%" align="left" valign="top">36.11. Library Functions </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 14.5 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 36.13. <acronym xmlns="http://www.w3.org/1999/xhtml" class="acronym">C++</acronym> Applications</td></tr></table></div></body></html>
\ No newline at end of file |