Merge branch 'on_error_stop' into 'master'

cause SQL scripts to stop immediately when unexpected errors occur

See merge request ifs/AngProj!11

0_runAllScripts.sql

@@ -60,3 +60,7 @@ CREATE DATABASE :database WITH OWNER :user ENCODING 'UTF8';
 -- query the database
 \ir 5_queries.sql
 
+\unset ECHO
+-- demonstrate constraints in action
+\ir 6_constraints_tests.sql
+

5_queries.sql

@@ -82,31 +82,3 @@ SELECT * FROM GutVerdienende;
 
 -- forget all changes made since BEGIN
 ROLLBACK;
-
--- Constraints Tests
-
--- do not alter contents of the database persistently
-BEGIN;
-
-ALTER TABLE Angestellter
-ADD CONSTRAINT check_Salaer
-   CHECK (Salaer between 1000 and 20000);
-   
-UPDATE angestellter SET salaer=30000 where persnr = 1100;
-select * from angestellter WHERE persnr = 1100;
-
--- forget all changes made since BEGIN
-ROLLBACK;
-
--- do not alter contents of the database persistently
-BEGIN;
-
-ALTER TABLE ProjektZuteilung
-ADD CONSTRAINT check_Zeitanteil
-   CHECK (Zeitanteil between 10 and 90);
-
-UPDATE ProjektZuteilung SET Zeitanteil=99 where persnr = 1100;
-select * from ProjektZuteilung WHERE persnr = 1100;
-
--- forget all changes made since BEGIN
-ROLLBACK;

6_constraints_tests.sql

+DO
+$$BEGIN
+   /* Exceptions of type integrity_constraint_violation within this block
+    * are intercepted and don't make the script fail.
+    */
+
+   -- Add a constraint:
+   ALTER TABLE Angestellter
+   ADD CONSTRAINT check_Salaer
+      CHECK (Salaer between 1000 and 20000);
+
+   -- Test the constraint:
+   UPDATE angestellter SET salaer=30000 where persnr = 1100;
+   /* The UPDATE above fails, thereby making execution jump
+    * into the EXCEPTION block below and causing a ROLLBACK
+    * of all changes within the block so far,
+    * incl. the addition of the constraint.
+    */
+
+   -- This exception is therefore never being raised:
+   RAISE EXCEPTION 'The constraint did not work.';
+EXCEPTION
+   WHEN integrity_constraint_violation THEN
+      -- Swallow the exception, but do print out its error message:
+      RAISE NOTICE 'The constraint worked and made the UPDATE fail with message: %', SQLERRM;
+END;$$;
+
+DO
+$$BEGIN
+   /* Exceptions of type integrity_constraint_violation within this block
+    * are intercepted and don't make the script fail.
+    */
+
+   -- Add a constraint:
+   ALTER TABLE ProjektZuteilung
+   ADD CONSTRAINT check_Zeitanteil
+      CHECK (Zeitanteil between 10 and 90);
+
+   -- Test the constraint:
+   UPDATE ProjektZuteilung SET Zeitanteil=99 where persnr = 1100;
+   /* The UPDATE above fails, thereby making execution jump
+    * into the EXCEPTION block below and causing a ROLLBACK
+    * of all changes within the block so far,
+    * incl. the addition of the constraint.
+    */
+
+   -- This exception is therefore never being raised:
+   RAISE EXCEPTION 'The constraint did not work.';
+EXCEPTION
+   WHEN integrity_constraint_violation THEN
+      -- Swallow the exception, but do print out its error message:
+      RAISE NOTICE 'The constraint worked and made the UPDATE fail with message: %', SQLERRM;
+END;$$;

README.md

@@ -142,7 +142,7 @@ Folgende Schritte werden dabei durchlaufen:
     ausgeführt werden):
 
     ``` bash
-    psql -U postgres -f 0_runAllScripts.sql
+    psql -U postgres -v ON_ERROR_STOP=on -f 0_runAllScripts.sql
     ```
 
     -   Windows
@@ -162,7 +162,7 @@ Folgende Schritte werden dabei durchlaufen:
         Datenbankbefehle auszuführen.
 
         ``` bash
-        sudo -u postgres psql -f 0_runAllScripts.sql
+        sudo -u postgres psql -v ON_ERROR_STOP=on -f 0_runAllScripts.sql
         ```
 
         Alternativ kann man sich für den Linux-Login einen

run.bat

 @echo off
 >nul chcp 1252
-psql -U postgres -f 0_runAllScripts.sql
+psql -U postgres -v ON_ERROR_STOP=on -f 0_runAllScripts.sql
 pause
\ No newline at end of file