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Add psql variables to track success/failure of SQL queries. 

This patch adds ERROR, SQLSTATE, and ROW_COUNT, which are updated after
every query, as well as LAST_ERROR_MESSAGE and LAST_ERROR_SQLSTATE,
which are updated only when a query fails.  The expected usage of these
is for scripting.

Fabien Coelho, reviewed by Pavel Stehule

Discussion: https://postgr.es/m/alpine.DEB.2.20.1704042158020.12290@lancre
This commit is contained in:
Tom Lane 2017-09-12 19:27:48 -04:00
parent 6e7baa3227
commit 69835bc898
6 changed files with 324 additions and 1 deletions
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44
doc/src/sgml/ref/psql-ref.sgml
View File

@ -3517,6 +3517,16 @@ bar
</listitem>
</varlistentry>
<varlistentry>
<term><varname>ERROR</varname></term>
<listitem>
<para>
<literal>true</> if the last SQL query failed, <literal>false</> if
it succeeded. See also <varname>SQLSTATE</>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>FETCH_COUNT</varname></term>
<listitem>
@ -3653,6 +3663,19 @@ bar
</listitem>
</varlistentry>
<varlistentry>
<term><varname>LAST_ERROR_MESSAGE</varname></term>
<term><varname>LAST_ERROR_SQLSTATE</varname></term>
<listitem>
<para>
The primary error message and associated SQLSTATE code for the most
recent failed query in the current <application>psql</> session, or
an empty string and <literal>00000</> if no error has occurred in
the current session.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
<varname>ON_ERROR_ROLLBACK</varname>
@ -3732,6 +3755,16 @@ bar
</listitem>
</varlistentry>
<varlistentry>
<term><varname>ROW_COUNT</varname></term>
<listitem>
<para>
The number of rows returned or affected by the last SQL query, or 0
if the query failed or did not report a row count.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>SERVER_VERSION_NAME</varname></term>
<term><varname>SERVER_VERSION_NUM</varname></term>
@ -3784,6 +3817,17 @@ bar
</listitem>
</varlistentry>
<varlistentry>
<term><varname>SQLSTATE</varname></term>
<listitem>
<para>
The error code (see <xref linkend="errcodes-appendix">) associated
with the last SQL query's failure, or <literal>00000</> if it
succeeded.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>USER</varname></term>
<listitem>

71
src/bin/psql/common.c
View File

@ -548,11 +548,58 @@ AcceptResult(const PGresult *result)
}
/*
* Set special variables from a query result
* - ERROR: true/false, whether an error occurred on this query
* - SQLSTATE: code of error, or "00000" if no error, or "" if unknown
* - ROW_COUNT: how many rows were returned or affected, or "0"
* - LAST_ERROR_SQLSTATE: same for last error
* - LAST_ERROR_MESSAGE: message of last error
*
* Note: current policy is to apply this only to the results of queries
* entered by the user, not queries generated by slash commands.
*/
static void
SetResultVariables(PGresult *results, bool success)
{
if (success)
{
const char *ntuples = PQcmdTuples(results);
SetVariable(pset.vars, "ERROR", "false");
SetVariable(pset.vars, "SQLSTATE", "00000");
SetVariable(pset.vars, "ROW_COUNT", *ntuples ? ntuples : "0");
}
else
{
const char *code = PQresultErrorField(results, PG_DIAG_SQLSTATE);
const char *mesg = PQresultErrorField(results, PG_DIAG_MESSAGE_PRIMARY);
SetVariable(pset.vars, "ERROR", "true");
/*
* If there is no SQLSTATE code, use an empty string. This can happen
* for libpq-detected errors (e.g., lost connection, ENOMEM).
*/
if (code == NULL)
code = "";
SetVariable(pset.vars, "SQLSTATE", code);
SetVariable(pset.vars, "ROW_COUNT", "0");
SetVariable(pset.vars, "LAST_ERROR_SQLSTATE", code);
SetVariable(pset.vars, "LAST_ERROR_MESSAGE", mesg ? mesg : "");
}
}
/*
* ClearOrSaveResult
*
* If the result represents an error, remember it for possible display by
* \errverbose. Otherwise, just PQclear() it.
*
* Note: current policy is to apply this to the results of all queries,
* including "back door" queries, for debugging's sake. It's OK to use
* PQclear() directly on results known to not be error results, however.
*/
static void
ClearOrSaveResult(PGresult *result)
@ -1107,6 +1154,8 @@ ProcessResult(PGresult **results)
first_cycle = false;
}
SetResultVariables(*results, success);
/* may need this to recover from conn loss during COPY */
if (!first_cycle && !CheckConnection())
return false;
@ -1526,6 +1575,7 @@ DescribeQuery(const char *query, double *elapsed_msec)
if (PQresultStatus(results) != PGRES_COMMAND_OK)
{
psql_error("%s", PQerrorMessage(pset.db));
SetResultVariables(results, false);
ClearOrSaveResult(results);
return false;
}
@ -1599,6 +1649,7 @@ DescribeQuery(const char *query, double *elapsed_msec)
_("The command has no result, or the result has no columns.\n"));
}
SetResultVariables(results, OK);
ClearOrSaveResult(results);
return OK;
@ -1626,6 +1677,7 @@ ExecQueryUsingCursor(const char *query, double *elapsed_msec)
bool is_pipe;
bool is_pager = false;
bool started_txn = false;
int64 total_tuples = 0;
int ntuples;
int fetch_count;
char fetch_cmd[64];
@ -1663,6 +1715,8 @@ ExecQueryUsingCursor(const char *query, double *elapsed_msec)
results = PQexec(pset.db, buf.data);
OK = AcceptResult(results) &&
(PQresultStatus(results) == PGRES_COMMAND_OK);
if (!OK)
SetResultVariables(results, OK);
ClearOrSaveResult(results);
termPQExpBuffer(&buf);
if (!OK)
@ -1738,6 +1792,7 @@ ExecQueryUsingCursor(const char *query, double *elapsed_msec)
OK = AcceptResult(results);
Assert(!OK);
SetResultVariables(results, OK);
ClearOrSaveResult(results);
break;
}
@ -1755,6 +1810,7 @@ ExecQueryUsingCursor(const char *query, double *elapsed_msec)
*/
ntuples = PQntuples(results);
total_tuples += ntuples;
if (ntuples < fetch_count)
{
@ -1816,6 +1872,21 @@ ExecQueryUsingCursor(const char *query, double *elapsed_msec)
ClosePager(fout);
}
if (OK)
{
/*
* We don't have a PGresult here, and even if we did it wouldn't have
* the right row count, so fake SetResultVariables(). In error cases,
* we already set the result variables above.
*/
char buf[32];
SetVariable(pset.vars, "ERROR", "false");
SetVariable(pset.vars, "SQLSTATE", "00000");
snprintf(buf, sizeof(buf), INT64_FORMAT, total_tuples);
SetVariable(pset.vars, "ROW_COUNT", buf);
}
cleanup:
if (pset.timing)
INSTR_TIME_SET_CURRENT(before);

11
src/bin/psql/help.c
View File

@ -337,7 +337,7 @@ helpVariables(unsigned short int pager)
* Windows builds currently print one more line than non-Windows builds.
* Using the larger number is fine.
*/
output = PageOutput(147, pager ? &(pset.popt.topt) : NULL);
output = PageOutput(156, pager ? &(pset.popt.topt) : NULL);
fprintf(output, _("List of specially treated variables\n\n"));
@ -360,6 +360,8 @@ helpVariables(unsigned short int pager)
" if set to \"noexec\", just show them without execution\n"));
fprintf(output, _(" ENCODING\n"
" current client character set encoding\n"));
fprintf(output, _(" ERROR\n"
" true if last query failed, else false\n"));
fprintf(output, _(" FETCH_COUNT\n"
" the number of result rows to fetch and display at a time (0 = unlimited)\n"));
fprintf(output, _(" HISTCONTROL\n"
@ -374,6 +376,9 @@ helpVariables(unsigned short int pager)
" number of EOFs needed to terminate an interactive session\n"));
fprintf(output, _(" LASTOID\n"
" value of the last affected OID\n"));
fprintf(output, _(" LAST_ERROR_MESSAGE\n"
" LAST_ERROR_SQLSTATE\n"
" message and SQLSTATE of last error, or empty string and \"00000\" if none\n"));
fprintf(output, _(" ON_ERROR_ROLLBACK\n"
" if set, an error doesn't stop a transaction (uses implicit savepoints)\n"));
fprintf(output, _(" ON_ERROR_STOP\n"
@ -388,6 +393,8 @@ helpVariables(unsigned short int pager)
" specifies the prompt used during COPY ... FROM STDIN\n"));
fprintf(output, _(" QUIET\n"
" run quietly (same as -q option)\n"));
fprintf(output, _(" ROW_COUNT\n"
" number of rows returned or affected by last query, or 0\n"));
fprintf(output, _(" SERVER_VERSION_NAME\n"
" SERVER_VERSION_NUM\n"
" server's version (in short string or numeric format)\n"));
@ -397,6 +404,8 @@ helpVariables(unsigned short int pager)
" if set, end of line terminates SQL commands (same as -S option)\n"));
fprintf(output, _(" SINGLESTEP\n"
" single-step mode (same as -s option)\n"));
fprintf(output, _(" SQLSTATE\n"
" SQLSTATE of last query, or \"00000\" if no error\n"));
fprintf(output, _(" USER\n"
" the currently connected database user\n"));
fprintf(output, _(" VERBOSITY\n"

4
src/bin/psql/startup.c
View File

@ -165,6 +165,10 @@ main(int argc, char *argv[])
SetVariable(pset.vars, "VERSION_NAME", PG_VERSION);
SetVariable(pset.vars, "VERSION_NUM", CppAsString2(PG_VERSION_NUM));
/* Initialize variables for last error */
SetVariable(pset.vars, "LAST_ERROR_MESSAGE", "");
SetVariable(pset.vars, "LAST_ERROR_SQLSTATE", "00000");
/* Default values for variables (that don't match the result of \unset) */
SetVariableBool(pset.vars, "AUTOCOMMIT");
SetVariable(pset.vars, "PROMPT1", DEFAULT_PROMPT1);

131
src/test/regress/expected/psql.out
View File

@ -3074,3 +3074,134 @@ SELECT 3
UNION SELECT 4
UNION SELECT 5
ORDER BY 1;
-- tests for special result variables
-- working query, 2 rows selected
SELECT 1 AS stuff UNION SELECT 2;
stuff
-------
1
2
(2 rows)
\echo 'error:' :ERROR
error: false
\echo 'error code:' :SQLSTATE
error code: 00000
\echo 'number of rows:' :ROW_COUNT
number of rows: 2
-- syntax error
SELECT 1 UNION;
ERROR: syntax error at or near ";"
LINE 1: SELECT 1 UNION;
^
\echo 'error:' :ERROR
error: true
\echo 'error code:' :SQLSTATE
error code: 42601
\echo 'number of rows:' :ROW_COUNT
number of rows: 0
\echo 'last error message:' :LAST_ERROR_MESSAGE
last error message: syntax error at or near ";"
\echo 'last error code:' :LAST_ERROR_SQLSTATE
last error code: 42601
-- empty query
;
\echo 'error:' :ERROR
error: false
\echo 'error code:' :SQLSTATE
error code: 00000
\echo 'number of rows:' :ROW_COUNT
number of rows: 0
-- must have kept previous values
\echo 'last error message:' :LAST_ERROR_MESSAGE
last error message: syntax error at or near ";"
\echo 'last error code:' :LAST_ERROR_SQLSTATE
last error code: 42601
-- other query error
DROP TABLE this_table_does_not_exist;
ERROR: table "this_table_does_not_exist" does not exist
\echo 'error:' :ERROR
error: true
\echo 'error code:' :SQLSTATE
error code: 42P01
\echo 'number of rows:' :ROW_COUNT
number of rows: 0
\echo 'last error message:' :LAST_ERROR_MESSAGE
last error message: table "this_table_does_not_exist" does not exist
\echo 'last error code:' :LAST_ERROR_SQLSTATE
last error code: 42P01
-- working \gdesc
SELECT 3 AS three, 4 AS four \gdesc
Column | Type
--------+---------
three | integer
four | integer
(2 rows)
\echo 'error:' :ERROR
error: false
\echo 'error code:' :SQLSTATE
error code: 00000
\echo 'number of rows:' :ROW_COUNT
number of rows: 2
-- \gdesc with an error
SELECT 4 AS \gdesc
ERROR: syntax error at end of input
LINE 1: SELECT 4 AS
^
\echo 'error:' :ERROR
error: true
\echo 'error code:' :SQLSTATE
error code: 42601
\echo 'number of rows:' :ROW_COUNT
number of rows: 0
\echo 'last error message:' :LAST_ERROR_MESSAGE
last error message: syntax error at end of input
\echo 'last error code:' :LAST_ERROR_SQLSTATE
last error code: 42601
-- check row count for a cursor-fetched query
\set FETCH_COUNT 10
select unique2 from tenk1 limit 19;
unique2
---------
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
(19 rows)
\echo 'error:' :ERROR
error: false
\echo 'error code:' :SQLSTATE
error code: 00000
\echo 'number of rows:' :ROW_COUNT
number of rows: 19
-- cursor-fetched query with an error
select 1/unique1 from tenk1;
ERROR: division by zero
\echo 'error:' :ERROR
error: true
\echo 'error code:' :SQLSTATE
error code: 22012
\echo 'number of rows:' :ROW_COUNT
number of rows: 0
\echo 'last error message:' :LAST_ERROR_MESSAGE
last error message: division by zero
\echo 'last error code:' :LAST_ERROR_SQLSTATE
last error code: 22012
\unset FETCH_COUNT

64
src/test/regress/sql/psql.sql
View File

@ -606,3 +606,67 @@ UNION SELECT 5
ORDER BY 1;
\r
\p
-- tests for special result variables
-- working query, 2 rows selected
SELECT 1 AS stuff UNION SELECT 2;
\echo 'error:' :ERROR
\echo 'error code:' :SQLSTATE
\echo 'number of rows:' :ROW_COUNT
-- syntax error
SELECT 1 UNION;
\echo 'error:' :ERROR
\echo 'error code:' :SQLSTATE
\echo 'number of rows:' :ROW_COUNT
\echo 'last error message:' :LAST_ERROR_MESSAGE
\echo 'last error code:' :LAST_ERROR_SQLSTATE
-- empty query
;
\echo 'error:' :ERROR
\echo 'error code:' :SQLSTATE
\echo 'number of rows:' :ROW_COUNT
-- must have kept previous values
\echo 'last error message:' :LAST_ERROR_MESSAGE
\echo 'last error code:' :LAST_ERROR_SQLSTATE
-- other query error
DROP TABLE this_table_does_not_exist;
\echo 'error:' :ERROR
\echo 'error code:' :SQLSTATE
\echo 'number of rows:' :ROW_COUNT
\echo 'last error message:' :LAST_ERROR_MESSAGE
\echo 'last error code:' :LAST_ERROR_SQLSTATE
-- working \gdesc
SELECT 3 AS three, 4 AS four \gdesc
\echo 'error:' :ERROR
\echo 'error code:' :SQLSTATE
\echo 'number of rows:' :ROW_COUNT
-- \gdesc with an error
SELECT 4 AS \gdesc
\echo 'error:' :ERROR
\echo 'error code:' :SQLSTATE
\echo 'number of rows:' :ROW_COUNT
\echo 'last error message:' :LAST_ERROR_MESSAGE
\echo 'last error code:' :LAST_ERROR_SQLSTATE
-- check row count for a cursor-fetched query
\set FETCH_COUNT 10
select unique2 from tenk1 limit 19;
\echo 'error:' :ERROR
\echo 'error code:' :SQLSTATE
\echo 'number of rows:' :ROW_COUNT
-- cursor-fetched query with an error
select 1/unique1 from tenk1;
\echo 'error:' :ERROR
\echo 'error code:' :SQLSTATE
\echo 'number of rows:' :ROW_COUNT
\echo 'last error message:' :LAST_ERROR_MESSAGE
\echo 'last error code:' :LAST_ERROR_SQLSTATE
\unset FETCH_COUNT