Add short interval unit notations h, m, s, d, w (#119)

ClickHouse supports short notations for interval units like
"INTERVAL 4 h" for hours. Added support for:
- h -> hour
- m -> minute
- s -> second
- d -> day
- w -> week
- ms -> millisecond
- us -> microsecond
- ns -> nanosecond

Updated both the parser's intervalUnits map and the explain code's
normalizeIntervalUnit functions to handle these short forms.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: kyleconroy

internal/explain/functions.go

@@ -22,20 +22,26 @@ func normalizeIntervalUnit(unit string) string {
 		u = u[8:] // Remove "sql_tsi_" prefix
 	}
 
-	// Handle SQL standard abbreviations
+	// Handle SQL standard abbreviations and ClickHouse short notations
 	abbrevs := map[string]string{
-		"yy":  "year",
-		"qq":  "quarter",
-		"mm":  "month",
-		"wk":  "week",
-		"ww":  "week",
-		"dd":  "day",
-		"hh":  "hour",
-		"mi":  "minute",
-		"ss":  "second",
-		"ms":  "millisecond",
-		"us":  "microsecond",
-		"ns":  "nanosecond",
+		"yy": "year",
+		"qq": "quarter",
+		"mm": "month",
+		"wk": "week",
+		"ww": "week",
+		"dd": "day",
+		"hh": "hour",
+		"mi": "minute",
+		"ss": "second",
+		// ClickHouse short notations
+		"w":  "week",
+		"d":  "day",
+		"h":  "hour",
+		"m":  "minute",
+		"s":  "second",
+		"ms": "millisecond",
+		"us": "microsecond",
+		"ns": "nanosecond",
 	}
 	if expanded, ok := abbrevs[u]; ok {
 		u = expanded
@@ -62,20 +68,26 @@ func normalizeIntervalUnitToLiteral(unit string) string {
 		u = u[8:] // Remove "sql_tsi_" prefix
 	}
 
-	// Handle SQL standard abbreviations
+	// Handle SQL standard abbreviations and ClickHouse short notations
 	abbrevs := map[string]string{
-		"yy":  "year",
-		"qq":  "quarter",
-		"mm":  "month",
-		"wk":  "week",
-		"ww":  "week",
-		"dd":  "day",
-		"hh":  "hour",
-		"mi":  "minute",
-		"ss":  "second",
-		"ms":  "millisecond",
-		"us":  "microsecond",
-		"ns":  "nanosecond",
+		"yy": "year",
+		"qq": "quarter",
+		"mm": "month",
+		"wk": "week",
+		"ww": "week",
+		"dd": "day",
+		"hh": "hour",
+		"mi": "minute",
+		"ss": "second",
+		// ClickHouse short notations
+		"w":  "week",
+		"d":  "day",
+		"h":  "hour",
+		"m":  "minute",
+		"s":  "second",
+		"ms": "millisecond",
+		"us": "microsecond",
+		"ns": "nanosecond",
 	}
 	if expanded, ok := abbrevs[u]; ok {
 		return expanded

parser/parser.go

@@ -18,14 +18,14 @@ var intervalUnits = map[string]bool{
 	"YEAR": true, "YEARS": true,
 	"QUARTER": true, "QUARTERS": true,
 	"MONTH": true, "MONTHS": true,
-	"WEEK": true, "WEEKS": true,
-	"DAY": true, "DAYS": true,
-	"HOUR": true, "HOURS": true,
-	"MINUTE": true, "MINUTES": true,
-	"SECOND": true, "SECONDS": true,
-	"MILLISECOND": true, "MILLISECONDS": true,
-	"MICROSECOND": true, "MICROSECONDS": true,
-	"NANOSECOND": true, "NANOSECONDS": true,
+	"WEEK": true, "WEEKS": true, "W": true,
+	"DAY": true, "DAYS": true, "D": true,
+	"HOUR": true, "HOURS": true, "H": true,
+	"MINUTE": true, "MINUTES": true, "M": true,
+	"SECOND": true, "SECONDS": true, "S": true,
+	"MILLISECOND": true, "MILLISECONDS": true, "MS": true,
+	"MICROSECOND": true, "MICROSECONDS": true, "US": true,
+	"NANOSECOND": true, "NANOSECONDS": true, "NS": true,
 }
 
 // isIntervalUnit checks if the given string is a valid interval unit name

parser/testdata/02360_small_notation_h_for_hour_interval/metadata.json

@@ -1 +1 @@
-{"explain_todo":{"stmt2":true}}
+{}