Editing IO behaviour (section)

== 3. Database I/O (primes.cbl via GixSQL) ==

<span id="connection-management"></span>
=== 3.1 Connection Management ===

{|
!width="33%"| Operation
!width="33%"| SQL
!width="33%"| Paragraph
|-
| Connect
| <code>CONNECT TO :DATASRC AS primes USER :DBUSR USING :DBPWD</code>
| s00-connect
|-
| Disconnect
| <code>CONNECT RESET primes</code>
| s99-disconnect
|}

Connection string: <code>pgsql://localhost:5432/primes&amp;default_schema=primes</code><br />
Connection alias: <code>primes</code> (used in all <code>EXEC SQL AT primes</code> statements)

<span id="cursor-lifecycle-report-path-only"></span>
=== 3.2 Cursor Lifecycle (report path only) ===

{|
!width="33%"| Operation
!width="33%"| SQL
!width="33%"| Paragraph
|-
| Declare
| <code>DECLARE primescursor CURSOR FOR SELECT * FROM primes</code>
| compile-time
|-
| Begin transaction
| <code>START TRANSACTION</code>
| s01-cursor
|-
| Open
| <code>OPEN primescursor</code>
| s01-cursor
|-
| Fetch one row
| <code>FETCH primescursor INTO :primes-row</code>
| s02-fetch
|-
| (Close)
| not explicitly closed — connection reset closes it
| —
|}

Each <code>FETCH</code> populates <code>primes-row</code> (r-ident, r-prime), which is then copied to <code>primes-sequence</code> and <code>prime-number</code> in <code>primes-dal</code> for the caller.

End-of-cursor is signalled by <code>SQLCODE ≠ 0</code>; <code>dal-result</code> is set to 1, which primesgen maps to <code>session-method-eof</code> implicitly (by checking <code>session-method-eof</code> condition, value 9 — note: there is a mapping gap; dal-result=1 does not equal session-result=9; the report loop relies on <code>session-method-eof</code> which is never explicitly set in the current code — see defect D-RPT-01 below).

<span id="dml-generate-path"></span>
=== 3.3 DML (generate path) ===

{|
!width="33%"| Operation
!width="33%"| SQL
!width="33%"| Paragraph
|-
| Insert prime
| <code>INSERT INTO primes (prime) VALUES (:prime)</code>
| r83-write-prime
|}

* Host variable <code>:prime</code> maps to <code>prime-number</code> in <code>primes-dal.primes-data</code>.
* No explicit COMMIT in the current code (statement is commented out).
* PostgreSQL default auto-commit applies per statement unless inside the transaction opened by <code>s01-cursor</code>.

<span id="queries-generate-path-divider-lookup"></span>
=== 3.4 Queries (generate path — divider lookup) ===

{|
!width="33%"| Operation
!width="33%"| SQL
!width="33%"| Paragraph
|-
| Get next divider
| <code>SELECT prime INTO :test-divider FROM primes WHERE ident = :new-ident</code>
| r81-get-next-divider
|}

* <code>:new-ident</code> = <code>old-ident + 1</code> (computed inline before the SELECT).
* <code>:test-divider</code> is in the local <code>primes</code> working-storage group in primesgen, not in <code>primes-dal</code>.

<span id="error-handling-pattern"></span>
=== 3.5 Error Handling Pattern ===

Every SQL statement uses the same pattern:

<pre>EXEC SQL ... END-EXEC
IF SQLCODE = 0 THEN
  [success actions]
ELSE
  [log error / set result code]</pre>
No <code>WHENEVER</code> directives are used.


-----

<span id="command-line-input"></span>