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diff --git a/doc/src/sgml/html/pltcl-error-handling.html b/doc/src/sgml/html/pltcl-error-handling.html new file mode 100644 index 0000000..0b470f8 --- /dev/null +++ b/doc/src/sgml/html/pltcl-error-handling.html @@ -0,0 +1,60 @@ +<?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>43.8. Error Handling in PL/Tcl</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 V1.79.1" /><link rel="prev" href="pltcl-event-trigger.html" title="43.7. Event Trigger Functions in PL/Tcl" /><link rel="next" href="pltcl-subtransactions.html" title="43.9. Explicit Subtransactions in PL/Tcl" /></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">43.8. Error Handling in PL/Tcl</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="pltcl-event-trigger.html" title="43.7. Event Trigger Functions in PL/Tcl">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="pltcl.html" title="Chapter 43. PL/Tcl — Tcl Procedural Language">Up</a></td><th width="60%" align="center">Chapter 43. PL/Tcl — Tcl Procedural Language</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 13.4 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="pltcl-subtransactions.html" title="43.9. Explicit Subtransactions in PL/Tcl">Next</a></td></tr></table><hr></hr></div><div class="sect1" id="PLTCL-ERROR-HANDLING"><div class="titlepage"><div><div><h2 class="title" style="clear: both">43.8. Error Handling in PL/Tcl</h2></div></div></div><a id="id-1.8.9.12.2" class="indexterm"></a><p> + Tcl code within or called from a PL/Tcl function can raise an error, + either by executing some invalid operation or by generating an error + using the Tcl <code class="function">error</code> command or + PL/Tcl's <code class="function">elog</code> command. Such errors can be caught + within Tcl using the Tcl <code class="function">catch</code> command. If an + error is not caught but is allowed to propagate out to the top level of + execution of the PL/Tcl function, it is reported as a SQL error in the + function's calling query. + </p><p> + Conversely, SQL errors that occur within PL/Tcl's + <code class="function">spi_exec</code>, <code class="function">spi_prepare</code>, + and <code class="function">spi_execp</code> commands are reported as Tcl errors, + so they are catchable by Tcl's <code class="function">catch</code> command. + (Each of these PL/Tcl commands runs its SQL operation in a + subtransaction, which is rolled back on error, so that any + partially-completed operation is automatically cleaned up.) + Again, if an error propagates out to the top level without being caught, + it turns back into a SQL error. + </p><p> + Tcl provides an <code class="varname">errorCode</code> variable that can represent + additional information about an error in a form that is easy for Tcl + programs to interpret. The contents are in Tcl list format, and the + first word identifies the subsystem or library reporting the error; + beyond that the contents are left to the individual subsystem or + library. For database errors reported by PL/Tcl commands, the first + word is <code class="literal">POSTGRES</code>, the second word is the PostgreSQL + version number, and additional words are field name/value pairs + providing detailed information about the error. + Fields <code class="varname">SQLSTATE</code>, <code class="varname">condition</code>, + and <code class="varname">message</code> are always supplied + (the first two represent the error code and condition name as shown + in <a class="xref" href="errcodes-appendix.html" title="Appendix A. PostgreSQL Error Codes">Appendix A</a>). + Fields that may be present include + <code class="varname">detail</code>, <code class="varname">hint</code>, <code class="varname">context</code>, + <code class="varname">schema</code>, <code class="varname">table</code>, <code class="varname">column</code>, + <code class="varname">datatype</code>, <code class="varname">constraint</code>, + <code class="varname">statement</code>, <code class="varname">cursor_position</code>, + <code class="varname">filename</code>, <code class="varname">lineno</code>, and + <code class="varname">funcname</code>. + </p><p> + A convenient way to work with PL/Tcl's <code class="varname">errorCode</code> + information is to load it into an array, so that the field names become + array subscripts. Code for doing that might look like +</p><pre class="programlisting"> +if {[catch { spi_exec $sql_command }]} { + if {[lindex $::errorCode 0] == "POSTGRES"} { + array set errorArray $::errorCode + if {$errorArray(condition) == "undefined_table"} { + # deal with missing table + } else { + # deal with some other type of SQL error + } + } +} +</pre><p> + (The double colons explicitly specify that <code class="varname">errorCode</code> + is a global variable.) + </p></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="pltcl-event-trigger.html" title="43.7. Event Trigger Functions in PL/Tcl">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="pltcl.html" title="Chapter 43. PL/Tcl — Tcl Procedural Language">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="pltcl-subtransactions.html" title="43.9. Explicit Subtransactions in PL/Tcl">Next</a></td></tr><tr><td width="40%" align="left" valign="top">43.7. Event Trigger Functions in PL/Tcl </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 13.4 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 43.9. Explicit Subtransactions in PL/Tcl</td></tr></table></div></body></html>
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