Include GUC's unit, if it has one, in out-of-range error messages.

This should reduce confusion in cases where we've applied a units
conversion, so that the number being reported (and the quoted range
limits) are in some other units than what the user gave in the
setting we're rejecting.

Some of the changes here assume that float GUCs can have units,
which isn't true just yet, but will be shortly.

Discussion: https://postgr.es/m/3811.1552169665@sss.pgh.pa.us

Author: tglsfdc

src/backend/utils/misc/guc.c

@@ -6038,6 +6038,54 @@ convert_from_base_unit(int64 base_value, int base_unit,
 	Assert(*unit != NULL);
 }
 
+/*
+ * Return the name of a GUC's base unit (e.g. "ms") given its flags.
+ * Return NULL if the GUC is unitless.
+ */
+static const char *
+get_config_unit_name(int flags)
+{
+	switch (flags & (GUC_UNIT_MEMORY | GUC_UNIT_TIME))
+	{
+		case 0:
+			return NULL;		/* GUC has no units */
+		case GUC_UNIT_BYTE:
+			return "B";
+		case GUC_UNIT_KB:
+			return "kB";
+		case GUC_UNIT_MB:
+			return "MB";
+		case GUC_UNIT_BLOCKS:
+			{
+				static char bbuf[8];
+
+				/* initialize if first time through */
+				if (bbuf[0] == '\0')
+					snprintf(bbuf, sizeof(bbuf), "%dkB", BLCKSZ / 1024);
+				return bbuf;
+			}
+		case GUC_UNIT_XBLOCKS:
+			{
+				static char xbuf[8];
+
+				/* initialize if first time through */
+				if (xbuf[0] == '\0')
+					snprintf(xbuf, sizeof(xbuf), "%dkB", XLOG_BLCKSZ / 1024);
+				return xbuf;
+			}
+		case GUC_UNIT_MS:
+			return "ms";
+		case GUC_UNIT_S:
+			return "s";
+		case GUC_UNIT_MIN:
+			return "min";
+		default:
+			elog(ERROR, "unrecognized GUC units value: %d",
+				 flags & (GUC_UNIT_MEMORY | GUC_UNIT_TIME));
+			return NULL;
+	}
+}
+
 
 /*
  * Try to parse value as an integer.  The accepted formats are the
@@ -6324,10 +6372,15 @@ parse_and_validate_value(struct config_generic *record,
 
 				if (newval->intval < conf->min || newval->intval > conf->max)
 				{
+					const char *unit = get_config_unit_name(conf->gen.flags);
+
 					ereport(elevel,
 							(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-							 errmsg("%d is outside the valid range for parameter \"%s\" (%d .. %d)",
-									newval->intval, name,
+							 errmsg("%d%s%s is outside the valid range for parameter \"%s\" (%d .. %d)",
+									newval->intval,
+									unit ? " " : "",
+									unit ? unit : "",
+									name,
 									conf->min, conf->max)));
 					return false;
 				}
@@ -6352,10 +6405,15 @@ parse_and_validate_value(struct config_generic *record,
 
 				if (newval->realval < conf->min || newval->realval > conf->max)
 				{
+					const char *unit = get_config_unit_name(conf->gen.flags);
+
 					ereport(elevel,
 							(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-							 errmsg("%g is outside the valid range for parameter \"%s\" (%g .. %g)",
-									newval->realval, name,
+							 errmsg("%g%s%s is outside the valid range for parameter \"%s\" (%g .. %g)",
+									newval->realval,
+									unit ? " " : "",
+									unit ? unit : "",
+									name,
 									conf->min, conf->max)));
 					return false;
 				}
@@ -8687,52 +8745,11 @@ GetConfigOptionByNum(int varnum, const char **values, bool *noshow)
 	/* name */
 	values[0] = conf->name;
 
-	/* setting : use _ShowOption in order to avoid duplicating the logic */
+	/* setting: use _ShowOption in order to avoid duplicating the logic */
 	values[1] = _ShowOption(conf, false);
 
-	/* unit */
-	if (conf->vartype == PGC_INT)
-	{
-		switch (conf->flags & (GUC_UNIT_MEMORY | GUC_UNIT_TIME))
-		{
-			case GUC_UNIT_BYTE:
-				values[2] = "B";
-				break;
-			case GUC_UNIT_KB:
-				values[2] = "kB";
-				break;
-			case GUC_UNIT_MB:
-				values[2] = "MB";
-				break;
-			case GUC_UNIT_BLOCKS:
-				snprintf(buffer, sizeof(buffer), "%dkB", BLCKSZ / 1024);
-				values[2] = pstrdup(buffer);
-				break;
-			case GUC_UNIT_XBLOCKS:
-				snprintf(buffer, sizeof(buffer), "%dkB", XLOG_BLCKSZ / 1024);
-				values[2] = pstrdup(buffer);
-				break;
-			case GUC_UNIT_MS:
-				values[2] = "ms";
-				break;
-			case GUC_UNIT_S:
-				values[2] = "s";
-				break;
-			case GUC_UNIT_MIN:
-				values[2] = "min";
-				break;
-			case 0:
-				values[2] = NULL;
-				break;
-			default:
-				elog(ERROR, "unrecognized GUC units value: %d",
-					 conf->flags & (GUC_UNIT_MEMORY | GUC_UNIT_TIME));
-				values[2] = NULL;
-				break;
-		}
-	}
-	else
-		values[2] = NULL;
+	/* unit, if any (NULL is fine) */
+	values[2] = get_config_unit_name(conf->flags);
 
 	/* group */
 	values[3] = _(config_group_names[conf->group]);

src/test/regress/expected/guc.out

@@ -510,7 +510,7 @@ SELECT '2006-08-13 12:34:56'::timestamptz;
 SET seq_page_cost TO 'NaN';
 ERROR:  parameter "seq_page_cost" requires a numeric value
 SET vacuum_cost_delay TO '10s';
-ERROR:  10000 is outside the valid range for parameter "vacuum_cost_delay" (0 .. 100)
+ERROR:  10000 ms is outside the valid range for parameter "vacuum_cost_delay" (0 .. 100)
 SET geqo_selection_bias TO '-infinity';
 ERROR:  -Infinity is outside the valid range for parameter "geqo_selection_bias" (1.5 .. 2)
 --