Convert domain_in to report errors softly.

This is straightforward as far as it goes.  However, it does not
attempt to trap errors occurring during the execution of domain
CHECK constraints.  Since those are general user-defined
expressions, the only way to do that would involve starting up a
subtransaction for each check.  Of course the entire point of
the soft-errors feature is to not need subtransactions, so that
would be self-defeating.  For now, we'll rely on the assumption
that domain checks are written to avoid throwing errors.

Discussion: https://postgr.es/m/1181028.1670635727@sss.pgh.pa.us

doc/src/sgml/ref/create_domain.sgml

@@ -239,6 +239,11 @@ INSERT INTO tab (domcol) VALUES ((SELECT domcol FROM tab WHERE false));
    DOMAIN</command>), adjust the function definition, and re-add the
    constraint, thereby rechecking it against stored data.
   </para>
+
+  <para>
+   It's also good practice to ensure that domain <literal>CHECK</literal>
+   expressions will not throw errors.
+  </para>
  </refsect1>
 
  <refsect1>

src/backend/utils/adt/domains.c

@@ -126,9 +126,14 @@ domain_state_setup(Oid domainType, bool binary, MemoryContext mcxt)
  * This is roughly similar to the handling of CoerceToDomain nodes in
  * execExpr*.c, but we execute each constraint separately, rather than
  * compiling them in-line within a larger expression.
+ *
+ * If escontext points to an ErrorStateContext, any failures are reported
+ * there, otherwise they are ereport'ed.  Note that we do not attempt to do
+ * soft reporting of errors raised during execution of CHECK constraints.
  */
 static void
-domain_check_input(Datum value, bool isnull, DomainIOData *my_extra)
+domain_check_input(Datum value, bool isnull, DomainIOData *my_extra,
+				   Node *escontext)
 {
 	ExprContext *econtext = my_extra->econtext;
 	ListCell   *l;
@@ -144,11 +149,14 @@ domain_check_input(Datum value, bool isnull, DomainIOData *my_extra)
 		{
 			case DOM_CONSTRAINT_NOTNULL:
 				if (isnull)
-					ereport(ERROR,
+				{
+					errsave(escontext,
 							(errcode(ERRCODE_NOT_NULL_VIOLATION),
 							 errmsg("domain %s does not allow null values",
 									format_type_be(my_extra->domain_type)),
 							 errdatatype(my_extra->domain_type)));
+					goto fail;
+				}
 				break;
 			case DOM_CONSTRAINT_CHECK:
 				{
@@ -179,13 +187,16 @@ domain_check_input(Datum value, bool isnull, DomainIOData *my_extra)
 					econtext->domainValue_isNull = isnull;
 
 					if (!ExecCheck(con->check_exprstate, econtext))
-						ereport(ERROR,
+					{
+						errsave(escontext,
 								(errcode(ERRCODE_CHECK_VIOLATION),
 								 errmsg("value for domain %s violates check constraint \"%s\"",
 										format_type_be(my_extra->domain_type),
 										con->name),
 								 errdomainconstraint(my_extra->domain_type,
 													 con->name)));
+						goto fail;
+					}
 					break;
 				}
 			default:
@@ -200,6 +211,7 @@ domain_check_input(Datum value, bool isnull, DomainIOData *my_extra)
 	 * per-tuple memory.  This avoids leaking non-memory resources, if
 	 * anything in the expression(s) has any.
 	 */
+fail:
 	if (econtext)
 		ReScanExprContext(econtext);
 }
@@ -213,6 +225,7 @@ domain_in(PG_FUNCTION_ARGS)
 {
 	char	   *string;
 	Oid			domainType;
+	Node	   *escontext = fcinfo->context;
 	DomainIOData *my_extra;
 	Datum		value;
 
@@ -245,15 +258,18 @@ domain_in(PG_FUNCTION_ARGS)
 	/*
 	 * Invoke the base type's typinput procedure to convert the data.
 	 */
-	value = InputFunctionCall(&my_extra->proc,
-							  string,
-							  my_extra->typioparam,
-							  my_extra->typtypmod);
+	if (!InputFunctionCallSafe(&my_extra->proc,
+							   string,
+							   my_extra->typioparam,
+							   my_extra->typtypmod,
+							   escontext,
+							   &value))
+		PG_RETURN_NULL();
 
 	/*
 	 * Do the necessary checks to ensure it's a valid domain value.
 	 */
-	domain_check_input(value, (string == NULL), my_extra);
+	domain_check_input(value, (string == NULL), my_extra, escontext);
 
 	if (string == NULL)
 		PG_RETURN_NULL();
@@ -309,7 +325,7 @@ domain_recv(PG_FUNCTION_ARGS)
 	/*
 	 * Do the necessary checks to ensure it's a valid domain value.
 	 */
-	domain_check_input(value, (buf == NULL), my_extra);
+	domain_check_input(value, (buf == NULL), my_extra, NULL);
 
 	if (buf == NULL)
 		PG_RETURN_NULL();
@@ -349,7 +365,7 @@ domain_check(Datum value, bool isnull, Oid domainType,
 	/*
 	 * Do the necessary checks to ensure it's a valid domain value.
 	 */
-	domain_check_input(value, isnull, my_extra);
+	domain_check_input(value, isnull, my_extra, NULL);
 }
 
 /*

src/test/regress/expected/domain.out

@@ -87,6 +87,56 @@ drop domain domainvarchar restrict;
 drop domain domainnumeric restrict;
 drop domain domainint4 restrict;
 drop domain domaintext;
+-- Test non-error-throwing input
+create domain positiveint int4 check(value > 0);
+create domain weirdfloat float8 check((1 / value) < 10);
+select pg_input_is_valid('1', 'positiveint');
+ pg_input_is_valid 
+-------------------
+ t
+(1 row)
+
+select pg_input_is_valid('junk', 'positiveint');
+ pg_input_is_valid 
+-------------------
+ f
+(1 row)
+
+select pg_input_is_valid('-1', 'positiveint');
+ pg_input_is_valid 
+-------------------
+ f
+(1 row)
+
+select pg_input_error_message('junk', 'positiveint');
+            pg_input_error_message             
+-----------------------------------------------
+ invalid input syntax for type integer: "junk"
+(1 row)
+
+select pg_input_error_message('-1', 'positiveint');
+                           pg_input_error_message                           
+----------------------------------------------------------------------------
+ value for domain positiveint violates check constraint "positiveint_check"
+(1 row)
+
+select pg_input_error_message('junk', 'weirdfloat');
+                 pg_input_error_message                 
+--------------------------------------------------------
+ invalid input syntax for type double precision: "junk"
+(1 row)
+
+select pg_input_error_message('0.01', 'weirdfloat');
+                          pg_input_error_message                          
+--------------------------------------------------------------------------
+ value for domain weirdfloat violates check constraint "weirdfloat_check"
+(1 row)
+
+-- We currently can't trap errors raised in the CHECK expression itself
+select pg_input_error_message('0', 'weirdfloat');
+ERROR:  division by zero
+drop domain positiveint;
+drop domain weirdfloat;
 -- Test domains over array types
 create domain domainint4arr int4[1];
 create domain domainchar4arr varchar(4)[2][3];

src/test/regress/sql/domain.sql

@@ -69,6 +69,25 @@ drop domain domainint4 restrict;
 drop domain domaintext;
 
 
+-- Test non-error-throwing input
+
+create domain positiveint int4 check(value > 0);
+create domain weirdfloat float8 check((1 / value) < 10);
+
+select pg_input_is_valid('1', 'positiveint');
+select pg_input_is_valid('junk', 'positiveint');
+select pg_input_is_valid('-1', 'positiveint');
+select pg_input_error_message('junk', 'positiveint');
+select pg_input_error_message('-1', 'positiveint');
+select pg_input_error_message('junk', 'weirdfloat');
+select pg_input_error_message('0.01', 'weirdfloat');
+-- We currently can't trap errors raised in the CHECK expression itself
+select pg_input_error_message('0', 'weirdfloat');
+
+drop domain positiveint;
+drop domain weirdfloat;
+
+
 -- Test domains over array types
 
 create domain domainint4arr int4[1];