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In PL/Tcl, make database errors return additional info in the errorCode.

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Tcl has a convention for returning additional info about an error in a
global variable named errorCode.  Up to now PL/Tcl has ignored that,
but this patch causes database errors caught by PL/Tcl to fill in
errorCode with useful information from the ErrorData struct.

Jim Nasby, reviewed by Pavel Stehule and myself
This commit is contained in:
Tom Lane 2016-03-25 15:52:53 -04:00
parent c94959d411
commit fb8d2a7f57
4 changed files with 272 additions and 5 deletions
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74
doc/src/sgml/pltcl.sgml
View File

@ -507,8 +507,9 @@ SELECT 'doesn''t' AS ret
written to the server log, or both is controlled by the
<xref linkend="guc-log-min-messages"> and
<xref linkend="guc-client-min-messages"> configuration
variables. See <xref linkend="runtime-config"> for more
information.
variables. See <xref linkend="runtime-config">
and <xref linkend="pltcl-error-handling">
for more information.
</para>
</listitem>
</varlistentry>
@ -775,6 +776,75 @@ CREATE EVENT TRIGGER tcl_a_snitch ON ddl_command_start EXECUTE PROCEDURE tclsnit
</para>
</sect1>
<sect1 id="pltcl-error-handling">
<title>Error Handling in PL/Tcl</title>
<indexterm>
<primary>exceptions</primary>
<secondary>in PL/Tcl</secondary>
</indexterm>
<para>
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 <function>error</function> command or
PL/Tcl's <function>elog</function> command. Such errors can be caught
within Tcl using the Tcl <function>catch</function> command. If they
are not caught but are allowed to propagate out to the top level of
execution of the PL/Tcl function, they turn into database errors.
</para>
<para>
Conversely, database errors that occur within PL/Tcl's
<function>spi_exec</function>, <function>spi_prepare</function>,
and <function>spi_execp</function> commands are reported as Tcl errors,
so they are catchable by Tcl's <function>catch</function> command.
Again, if they propagate out to the top level without being caught,
they turn back into database errors.
</para>
<para>
Tcl provides an <varname>errorCode</varname> 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 <literal>POSTGRES</literal>, the second word is the Postgres
version number, and additional words are field name/value pairs
providing detailed information about the error.
Fields <varname>message</> and <varname>SQLSTATE</> (the error code
shown in <xref linkend="errcodes-appendix">) are always supplied.
Fields that may be present include
<varname>detail</>, <varname>hint</>, <varname>context</>,
<varname>schema</>, <varname>table</>, <varname>column</>,
<varname>datatype</>, <varname>constraint</>,
<varname>statement</>, <varname>cursor_position</>,
<varname>filename</>, <varname>lineno</> and
<varname>funcname</>.
</para>
<para>
A convenient way to work with PL/Tcl's <varname>errorCode</varname>
information is to load it into an array, so that the field names become
array subscripts. Code for doing that might look like
<programlisting>
if {[catch { spi_exec $sql_command }]} {
if {[lindex $::errorCode 0] == "POSTGRES"} {
array set errorArray $::errorCode
if {$errorArray(SQLSTATE) == "42P01"} { # UNDEFINED_TABLE
# deal with missing table
} else {
# deal with some other type of SQL error
}
}
}
</programlisting>
(The double colons explicitly specify that <varname>errorCode</varname>
is a global variable.)
</para>
</sect1>
<sect1 id="pltcl-unknown">
<title>Modules and the <function>unknown</> Command</title>
<para>

28
src/pl/tcl/expected/pltcl_setup.out
View File

@ -555,3 +555,31 @@ NOTICE: tclsnitch: ddl_command_start DROP TABLE
NOTICE: tclsnitch: ddl_command_end DROP TABLE
drop event trigger tcl_a_snitch;
drop event trigger tcl_b_snitch;
-- test use of errorCode in error handling
create function tcl_error_handling_test() returns text as $$
global errorCode
if {[catch { spi_exec "select no_such_column from foo;" }]} {
array set errArray $errorCode
if {$errArray(SQLSTATE) == "42P01"} {
return "expected error: $errArray(message)"
} else {
return "unexpected error: $errArray(SQLSTATE) $errArray(message)"
}
} else {
return "no error"
}
$$ language pltcl;
select tcl_error_handling_test();
tcl_error_handling_test
-----------------------------------------------
expected error: relation "foo" does not exist
(1 row)
create temp table foo(f1 int);
select tcl_error_handling_test();
tcl_error_handling_test
----------------------------------------------------------------
unexpected error: 42703 column "no_such_column" does not exist
(1 row)
drop table foo;

151
src/pl/tcl/pltcl.c
View File

@ -212,6 +212,7 @@ static pltcl_proc_desc *compile_pltcl_function(Oid fn_oid, Oid tgreloid,
static int pltcl_elog(ClientData cdata, Tcl_Interp *interp,
int objc, Tcl_Obj *const objv[]);
static void pltcl_construct_errorCode(Tcl_Interp *interp, ErrorData *edata);
static int pltcl_quote(ClientData cdata, Tcl_Interp *interp,
int objc, Tcl_Obj *const objv[]);
static int pltcl_argisnull(ClientData cdata, Tcl_Interp *interp,
@ -1648,7 +1649,8 @@ pltcl_elog(ClientData cdata, Tcl_Interp *interp,
edata = CopyErrorData();
FlushErrorState();
/* Pass the error message to Tcl */
/* Pass the error data to Tcl */
pltcl_construct_errorCode(interp, edata);
UTF_BEGIN;
Tcl_SetObjResult(interp, Tcl_NewStringObj(UTF_E2U(edata->message), -1));
UTF_END;
@ -1662,6 +1664,148 @@ pltcl_elog(ClientData cdata, Tcl_Interp *interp,
}
/**********************************************************************
* pltcl_construct_errorCode() - construct a Tcl errorCode
* list with detailed information from the PostgreSQL server
**********************************************************************/
static void
pltcl_construct_errorCode(Tcl_Interp *interp, ErrorData *edata)
{
Tcl_Obj *obj = Tcl_NewObj();
Tcl_ListObjAppendElement(interp, obj,
Tcl_NewStringObj("POSTGRES", -1));
Tcl_ListObjAppendElement(interp, obj,
Tcl_NewStringObj(PG_VERSION, -1));
Tcl_ListObjAppendElement(interp, obj,
Tcl_NewStringObj("SQLSTATE", -1));
Tcl_ListObjAppendElement(interp, obj,
Tcl_NewStringObj(unpack_sql_state(edata->sqlerrcode), -1));
Tcl_ListObjAppendElement(interp, obj,
Tcl_NewStringObj("message", -1));
UTF_BEGIN;
Tcl_ListObjAppendElement(interp, obj,
Tcl_NewStringObj(UTF_E2U(edata->message), -1));
UTF_END;
if (edata->detail)
{
Tcl_ListObjAppendElement(interp, obj,
Tcl_NewStringObj("detail", -1));
UTF_BEGIN;
Tcl_ListObjAppendElement(interp, obj,
Tcl_NewStringObj(UTF_E2U(edata->detail), -1));
UTF_END;
}
if (edata->hint)
{
Tcl_ListObjAppendElement(interp, obj,
Tcl_NewStringObj("hint", -1));
UTF_BEGIN;
Tcl_ListObjAppendElement(interp, obj,
Tcl_NewStringObj(UTF_E2U(edata->hint), -1));
UTF_END;
}
if (edata->context)
{
Tcl_ListObjAppendElement(interp, obj,
Tcl_NewStringObj("context", -1));
UTF_BEGIN;
Tcl_ListObjAppendElement(interp, obj,
Tcl_NewStringObj(UTF_E2U(edata->context), -1));
UTF_END;
}
if (edata->schema_name)
{
Tcl_ListObjAppendElement(interp, obj,
Tcl_NewStringObj("schema", -1));
UTF_BEGIN;
Tcl_ListObjAppendElement(interp, obj,
Tcl_NewStringObj(UTF_E2U(edata->schema_name), -1));
UTF_END;
}
if (edata->table_name)
{
Tcl_ListObjAppendElement(interp, obj,
Tcl_NewStringObj("table", -1));
UTF_BEGIN;
Tcl_ListObjAppendElement(interp, obj,
Tcl_NewStringObj(UTF_E2U(edata->table_name), -1));
UTF_END;
}
if (edata->column_name)
{
Tcl_ListObjAppendElement(interp, obj,
Tcl_NewStringObj("column", -1));
UTF_BEGIN;
Tcl_ListObjAppendElement(interp, obj,
Tcl_NewStringObj(UTF_E2U(edata->column_name), -1));
UTF_END;
}
if (edata->datatype_name)
{
Tcl_ListObjAppendElement(interp, obj,
Tcl_NewStringObj("datatype", -1));
UTF_BEGIN;
Tcl_ListObjAppendElement(interp, obj,
Tcl_NewStringObj(UTF_E2U(edata->datatype_name), -1));
UTF_END;
}
if (edata->constraint_name)
{
Tcl_ListObjAppendElement(interp, obj,
Tcl_NewStringObj("constraint", -1));
UTF_BEGIN;
Tcl_ListObjAppendElement(interp, obj,
Tcl_NewStringObj(UTF_E2U(edata->constraint_name), -1));
UTF_END;
}
/* cursorpos is never interesting here; report internal query/pos */
if (edata->internalquery)
{
Tcl_ListObjAppendElement(interp, obj,
Tcl_NewStringObj("statement", -1));
UTF_BEGIN;
Tcl_ListObjAppendElement(interp, obj,
Tcl_NewStringObj(UTF_E2U(edata->internalquery), -1));
UTF_END;
}
if (edata->internalpos > 0)
{
Tcl_ListObjAppendElement(interp, obj,
Tcl_NewStringObj("cursor_position", -1));
Tcl_ListObjAppendElement(interp, obj,
Tcl_NewIntObj(edata->internalpos));
}
if (edata->filename)
{
Tcl_ListObjAppendElement(interp, obj,
Tcl_NewStringObj("filename", -1));
UTF_BEGIN;
Tcl_ListObjAppendElement(interp, obj,
Tcl_NewStringObj(UTF_E2U(edata->filename), -1));
UTF_END;
}
if (edata->lineno > 0)
{
Tcl_ListObjAppendElement(interp, obj,
Tcl_NewStringObj("lineno", -1));
Tcl_ListObjAppendElement(interp, obj,
Tcl_NewIntObj(edata->lineno));
}
if (edata->funcname)
{
Tcl_ListObjAppendElement(interp, obj,
Tcl_NewStringObj("funcname", -1));
UTF_BEGIN;
Tcl_ListObjAppendElement(interp, obj,
Tcl_NewStringObj(UTF_E2U(edata->funcname), -1));
UTF_END;
}
Tcl_SetObjErrorCode(interp, obj);
}
/**********************************************************************
* pltcl_quote() - quote literal strings that are to
* be used in SPI_execute query strings
@ -1880,9 +2024,10 @@ pltcl_subtrans_abort(Tcl_Interp *interp,
*/
SPI_restore_connection();
/* Pass the error message to Tcl */
/* Pass the error data to Tcl */
pltcl_construct_errorCode(interp, edata);
UTF_BEGIN;
Tcl_SetResult(interp, UTF_E2U(edata->message), TCL_VOLATILE);
Tcl_SetObjResult(interp, Tcl_NewStringObj(UTF_E2U(edata->message), -1));
UTF_END;
FreeErrorData(edata);
}

24
src/pl/tcl/sql/pltcl_setup.sql
View File

@ -595,3 +595,27 @@ drop table foo;
drop event trigger tcl_a_snitch;
drop event trigger tcl_b_snitch;
-- test use of errorCode in error handling
create function tcl_error_handling_test() returns text as $$
global errorCode
if {[catch { spi_exec "select no_such_column from foo;" }]} {
array set errArray $errorCode
if {$errArray(SQLSTATE) == "42P01"} {
return "expected error: $errArray(message)"
} else {
return "unexpected error: $errArray(SQLSTATE) $errArray(message)"
}
} else {
return "no error"
}
$$ language pltcl;
select tcl_error_handling_test();
create temp table foo(f1 int);
select tcl_error_handling_test();
drop table foo;