Stuart Kendrick wrote:
hi,

i'm looking for trouble-shooting pointers, particularly around how to
debug query results

on one host, i have a PHP reporting tool querying a PostGres back-end.
Recently (i must have changed something ... but ... i don't remember
even logging into this box recently, let alone changing anything),
reports starting returning zero rows

however, when i point the reporting front-end at another back-end host
(the development box), the reports contain results.  the results even
look correct ;)

when i run 'psql' on the production box and manually enter SELECT
statements, i see results.  those results look awfully similar to the
results i see when i point my reporting front-end at the development box
back-end ;)


here's a window into my code:

[...]
  echo "<p>$sql</p>";

  # Query Soma
  $dbh = connect_db();
  $q   = query_db($dbh, $sql, $place);

  # Find metadata
  $num_hosts = $q->numRows();
  DB::isError($q) and die ($q->getMessage());
  echo "<p># of Records = $num_hosts</p>";

  # Generate and print the table
  generate_table($q);
[...]

function connect_db () {
  $dsn = 'pgsql://foo:[EMAIL PROTECTED]/soma';
  $dbh = DB::connect($dsn, array('debug' => 1));
  DB::isError($dbh) and die ($dbh->getMessage());
  return $dbh;
}

function query_db ($dbh, $sql, $place) {
  $q = $dbh->query($sql, $place);
  DB::isError($q) and die ($q->getMessage());
  return $q;
}
[...]


when i perform a manual query via psql, i get results:

soma=# SELECT mac, ip_addr, vlan, ad_ou, current_os_user, os_hostname,
dns_hostname, version_name, snmp_sys_descr, snmp_sys_objectid,
first_seen, last_seen, last_updated FROM hosts LEFT JOIN os_versions ON
hosts.osver = os_versions.versionid WHERE last_seen > 2006-08-14 AND
vlan = 74 ORDER BY ip_addr ASC;
[...results...]

but when i run a query using my PHP front-end, i don't. the debug output
(echo stmts) to my browser looks like this:

Querying Soma for Vlan = 74 WHERE Last_seen > 2006-08-14

SELECT mac, ip_addr, vlan, ad_ou, current_os_user, os_hostname,
dns_hostname, version_name, snmp_sys_descr, snmp_sys_objectid,
first_seen, last_seen, last_updated FROM hosts LEFT JOIN os_versions ON
hosts.osver = os_versions.versionid WHERE last_seen > ? AND vlan = ?
ORDER BY ip_addr ASC

# of Records = 0

Zero records.  No output.  As though the database were empty.  i've run
a bunch of queries ... my reporting front-end allows me to produce a
dozen or so reports ... and they all return 0 records



ok, so i enabled postgres' statement logging capability in postgresql.conf:
[...]
log_statement = 'all'
[...]

here's what i see when i perform a manual 'psql' query:


Sep 13 10:29:09 starsha postgres[24143]: [2-1] LOG:  connection
received: host=[local]
Sep 13 10:29:09 starsha postgres[24143]: [3-1] LOG:  connection
authorized: user=foo database=soma
Sep 13 10:29:31 starsha postgres[24143]: [4-1] LOG:  statement: SELECT
mac, ip_addr, vlan, ad_ou, current_os_user, os_hostname, dns_hostname,
version_name, snmp_sys_descr,
Sep 13 10:29:31 starsha postgres[24143]: [4-2]  snmp_sys_objectid,
first_seen, last_seen, last_updated FROM hosts LEFT JOIN os_versions ON
hosts.osver = os_versions.versionid
Sep 13 10:29:31 starsha postgres[24143]: [4-3]  WHERE last_seen >
2006-08-14 AND vlan = 74 ORDER BY ip_addr ASC;
Sep 13 10:29:32 starsha postgres[24143]: [5-1] LOG:  duration: 93.679 ms
Sep 13 10:29:53 starsha postgres[24143]: [6-1] LOG:  disconnection:
session time: 0:00:43.95 user=foo database=soma host=[local]


and here's what i see when my PHP code performs the query:

Sep 13 10:24:26 starsha postgres[24115]: [2-1] LOG:  connection
received: host=starsha.fhcrc.org port=50184
Sep 13 10:24:26 starsha postgres[24115]: [3-1] LOG:  connection
authorized: user=foo database=soma
Sep 13 10:24:26 starsha postgres[24115]: [4-1] LOG:  statement: SELECT
mac, ip_addr, vlan, ad_ou, current_os_user, os_hostname, ^M
Sep 13 10:24:26 starsha postgres[24115]: [4-2]
dns_hostname, version_name, snmp_sys_descr, ^M
Sep 13 10:24:26 starsha postgres[24115]: [4-3]
snmp_sys_objectid, first_seen, last_seen, last_updated FROM hosts LEFT
JOIN os_versions ON hosts.osver =
Sep 13 10:24:26 starsha postgres[24115]: [4-4]  os_versions.versionid
WHERE last_seen > '2006-08-14' AND vlan = '74' ORDER BY ip_addr ASC
Sep 13 10:24:26 starsha postgres[24115]: [5-1] LOG:  duration: 34.641 ms
Sep 13 10:24:26 starsha postgres[24115]: [6-1] LOG:  disconnection:
session time: 0:00:00.10 user=foo database=soma
host=production.company.com port=50184


those '^M' look suspicious ... and so do the single quotes around
2006-08-14 and 74 ... when i try typing single quotes into a manual psql
query, i get nothing in response.  could this be a symptom of the problem?

^M's are newlines, nothing to worry about.

So if you do the same query with & without the quotes it behaves differently?

SELECT mac, ip_addr, vlan, ad_ou, current_os_user, os_hostname,
dns_hostname, version_name, snmp_sys_descr, snmp_sys_objectid,
first_seen, last_seen, last_updated FROM hosts LEFT JOIN os_versions ON
hosts.osver = os_versions.versionid WHERE last_seen > 2006-08-14 AND
vlan = 74 ORDER BY ip_addr ASC;

vs

SELECT mac, ip_addr, vlan, ad_ou, current_os_user, os_hostname,
dns_hostname, version_name, snmp_sys_descr, snmp_sys_objectid,
first_seen, last_seen, last_updated FROM hosts LEFT JOIN os_versions ON
hosts.osver = os_versions.versionid WHERE last_seen > '2006-08-14' AND
vlan = '74' ORDER BY ip_addr ASC;

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