Here's a tricky one:
Versions: I'm using PostgreSQL 9.0.7 and PHP 5.3.8.

First, I have a table "bob" with two columns: "bobid" (integer) and "bobtext" (text). The "bobid" field defaults to a sequence called "bob_seq" which is just a simple counter (1,2,3 etc.)

I can do an INSERT query into "bob":

  INSERT INTO bob (bobtext) VALUES ('Hello Bob') RETURNING bobid;

and get the value the sequence has given me for "bobid": this works fine using both the psql tool and pg_query in PHP.

I can also do an UPDATE query in the same vein:

  UPDATE bob SET bobtext='Hello Bob revisited' WHERE bobid=<x> RETURNING bobid;

where <x> is a valid "bobid" value for an existing record in the table. This returns the value of "bobid" for the updated record which should be the same as <x> and again it works in the psql tool and in pg_query.

Next, I have a VIEW based on "bob", called "fred". It is simply defined as

    SELECT * FROM bob

I have two rules on "fred" which allow me to alter the view.
The first is used for INSERT into "fred", which translates them into INSERT into "bob":

    ON INSERT TO fred
      INSERT INTO bob (bobtext) VALUES (NEW.bobtext) RETURNING *

The second is used for UPDATE on "fred", which translates to creating a new record in "bob" and deleting the old record:

    ON UPDATE TO fred
      INSERT INTO bob (bobtext) VALUES (NEW.bobtext) RETURNING *;
      DELETE FROM bob WHERE bobid=OLD.bobid;

Note that these rules both return all of the fields of the newly inserted "bob" records back up the chain to be accessible to the original query.

Now, I can insert into "fred" knowing that the rule will handle it:

  INSERT INTO fred (bobtext) VALUES ('Hello Fred') RETURNING bobid;

and that should return the new "bobid" value of the inserted record (from the "bob_seq" sequence). It still works in the psql tool and in pg_query.

I should also be able to exercise the update rule on "fred":

  UPDATE fred SET bobtext='Hello Fred revisited' WHERE bobid=<x> RETURNING bobid

where <x> is a valid "bobid" value for an existing record in the table.
This should insert a new row with a new "bobid" from the sequence and the new "bobtext" value, delete the row with "bobid"=<x>, and return the "bobid" for the new row.

Here's the punchline (at last):
It works in the psql tool.
It doesn't work in pg_query.

$result = pg_query("UPDATE fred SET bobtext='Hello Fred revisited' WHERE bobid=42 RETURNING bobid"); // Assume there is a record with bobid==42
   if ($result && pg_numrows($result))
       echo pg_numrows($result).PHP_EOL;
       echo pg_fetch_result($result, 0, 0).PHP_EOL;

Tells me there that although the $result resource is valid, there are no rows and therefore no result to fetch (PHP Warning: pg_fetch_result(): Unable to jump to row 0 on PostgreSQL result ...)

So: why is the return from the UPDATE rule different to the return from the INSERT rule in PHP pgsql?

Thanks for taking the time...


Peter Ford, Developer                 phone: 01580 893333 fax: 01580 893399
Justcroft International Ltd.                    
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