Date: Wed, 18 Aug 2021 12:17:03 -0400
From: Bruce Momjian <bruce@momjian.us>
To: andrew@andrewculver.com, pgsql-docs@lists.postgresql.org
Subject: Re: ECPG cursor examples should include EXEC SQL WHENEVER NOT FOUND
 CONTINUE; after the while loop
Message-ID: <20210818161703.GC13002@momjian.us>
References: <162531325118.701.13401788614496956581@wrigleys.postgresql.org>
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On Sat, Jul  3, 2021 at 11:54:11AM +0000, PG Doc comments form wrote:
> The following documentation comment has been logged on the website:
> 
> Page: https://www.postgresql.org/docs/13/ecpg-variables.html
> Description:
> 
> Without this line:
> EXEC SQL WHENEVER NOT FOUND CONTINUE;
> after the while(1), I find that ECPG CURSOR examples fail.
> 
> For example, this example under 36.4.4.3.2. Structures fails:

Uh, can you give me full C example to test?  I already see EXEC SQL
WHENEVER NOT FOUND DO BREAK in the sample code, so I don't see how
CONTINUE would actually work, since it would just loop over the result
infinitely.

---------------------------------------------------------------------------

> 
> EXEC SQL BEGIN DECLARE SECTION;
>     typedef struct
>     {
>        int oid;
>        char datname[65];
>        long long int size;
>     } dbinfo_t;
> 
>     dbinfo_t dbval;
> EXEC SQL END DECLARE SECTION;
> 
>     memset(&dbval, 0, sizeof(dbinfo_t));
> 
>     EXEC SQL DECLARE cur1 CURSOR FOR SELECT oid, datname,
> pg_database_size(oid) AS size FROM pg_database;
>     EXEC SQL OPEN cur1;
> 
>     /* when end of result set reached, break out of while loop */
>     EXEC SQL WHENEVER NOT FOUND DO BREAK;
> 
>     while (1)
>     {
>         /* Fetch multiple columns into one structure. */
>         EXEC SQL FETCH FROM cur1 INTO :dbval;
> 
>         /* Print members of the structure. */
>         printf("oid=%d, datname=%s, size=%lld\n", dbval.oid, dbval.datname,
> dbval.size);
>     }
> 
>     EXEC SQL CLOSE cur1;


-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EDB                                      https://enterprisedb.com

  If only the physical world exists, free will is an illusion.