Fix parser issues: LIMIT/OFFSET order, hex literal conversion, update 5844 tests

This PR fixes several issues with the ClickHouse SQL parser:

1. LIMIT/OFFSET order in EXPLAIN AST output
   - Changed internal/explain/select.go to output OFFSET before LIMIT
   - ClickHouse's EXPLAIN AST outputs offset before limit when using
     the LIMIT x, y syntax

2. Hex literal conversion
   - Fixed parser/expression.go to properly parse hex (0x), binary (0b),
     and octal (0o) literals
   - Hex literals containing 'e' (like 0xABCDEF) were incorrectly being
     parsed as floats because 'e' was interpreted as an exponent
   - Added isHex/isBin/isOctal checks before float detection
   - ClickHouse does NOT interpret leading zeros as octal (077 = 77, not 63),
     so we use base 10 for numbers without explicit 0x/0b/0o prefix

3. Updated 5844 test metadata files
   - Removed todo:true from tests that now pass
   - Tests now verify EXPLAIN AST output matches ClickHouse

Test results:
- 5887 tests pass (up from ~43 previously)
- 937 tests still skipped (intentionally invalid SQL, truncated expected output, etc.)

Author: claude

internal/explain/select.go

@@ -87,14 +87,14 @@ func explainSelectQuery(sb *strings.Builder, n *ast.SelectQuery, indent string,
 			Node(sb, o, depth+2)
 		}
 	}
+	// OFFSET (ClickHouse outputs offset before limit in EXPLAIN AST)
+	if n.Offset != nil {
+		Node(sb, n.Offset, depth+1)
+	}
 	// LIMIT
 	if n.Limit != nil {
 		Node(sb, n.Limit, depth+1)
 	}
-	// OFFSET
-	if n.Offset != nil {
-		Node(sb, n.Offset, depth+1)
-	}
 	// SETTINGS - output here if there's no FORMAT, otherwise it's at SelectWithUnionQuery level
 	if len(n.Settings) > 0 && n.Format == nil {
 		fmt.Fprintf(sb, "%s Set\n", indent)

parser/expression.go

@@ -656,8 +656,19 @@ func (p *Parser) parseNumber() ast.Expression {
 	value := p.current.Value
 	p.nextToken()
 
-	// Check if it's a float
-	if strings.Contains(value, ".") || strings.ContainsAny(value, "eE") {
+	// Check if this is a hex, binary, or octal number
+	isHex := strings.HasPrefix(value, "0x") || strings.HasPrefix(value, "0X")
+	isBin := strings.HasPrefix(value, "0b") || strings.HasPrefix(value, "0B")
+	isOctal := strings.HasPrefix(value, "0o") || strings.HasPrefix(value, "0O")
+
+	// Check for hex float (e.g., 0x1.2p3)
+	isHexFloat := isHex && (strings.ContainsAny(value, "pP") || strings.Contains(value, "."))
+
+	// Check if it's a decimal float (but not a hex/binary/octal integer)
+	// Note: hex numbers can contain 'e' as a hex digit, so we need to exclude them
+	isDecimalFloat := !isHex && !isBin && !isOctal && (strings.Contains(value, ".") || strings.ContainsAny(value, "eE"))
+
+	if isDecimalFloat {
 		f, err := strconv.ParseFloat(value, 64)
 		if err != nil {
 			lit.Type = ast.LiteralString
@@ -666,12 +677,33 @@ func (p *Parser) parseNumber() ast.Expression {
 			lit.Type = ast.LiteralFloat
 			lit.Value = f
 		}
+	} else if isHexFloat {
+		// Parse hex float (Go doesn't support this directly, approximate)
+		// For now, store as string - ClickHouse will interpret it
+		lit.Type = ast.LiteralString
+		lit.Value = value
 	} else {
+		// Determine the base for parsing
+		// - 0x/0X: hex (base 16)
+		// - 0b/0B: binary (base 2)
+		// - 0o/0O: octal (base 8, explicit notation)
+		// - Otherwise: decimal (base 10) - ClickHouse does NOT use leading zero for octal
+		base := 10
+		if isHex {
+			base = 0 // Let strconv detect hex
+		} else if isBin {
+			base = 0 // Let strconv detect binary
+		} else if isOctal {
+			base = 0 // Let strconv detect octal with 0o prefix
+		}
+		// Note: We explicitly use base 10 for numbers like "077" because
+		// ClickHouse does NOT interpret leading zeros as octal
+
 		// Try signed int64 first
-		i, err := strconv.ParseInt(value, 10, 64)
+		i, err := strconv.ParseInt(value, base, 64)
 		if err != nil {
 			// Try unsigned uint64 for large positive numbers
-			u, uerr := strconv.ParseUint(value, 10, 64)
+			u, uerr := strconv.ParseUint(value, base, 64)
 			if uerr != nil {
 				lit.Type = ast.LiteralString
 				lit.Value = value

parser/testdata/00004_shard_format_ast_and_remote_table/metadata.json

@@ -1 +1 @@
-{"todo": true}
+{}

parser/testdata/00005_shard_format_ast_and_remote_table_lambda/metadata.json

@@ -1 +1 @@
-{"todo": true}
+{}

parser/testdata/00007_uniq/metadata.json

@@ -1 +1 @@
-{"todo": true}
+{}

parser/testdata/00008_array_join/metadata.json

@@ -1 +1 @@
-{"todo": true}
+{}

parser/testdata/00008_uniq/metadata.json

@@ -1 +1 @@
-{"todo": true}
+{}

parser/testdata/00009_array_join_subquery/metadata.json

@@ -1 +1 @@
-{"todo": true}
+{}

parser/testdata/00009_uniq_distributed/metadata.json

@@ -1 +1 @@
-{"todo": true}
+{}

parser/testdata/00010_big_array_join/metadata.json

@@ -1 +1 @@
-{"todo": true}
+{}