refactor: optimize SQL parser with caching and simplified state machine

Author: rusher

mariadb/impl/sql_parser.py

@@ -14,94 +14,78 @@
 Based on mariadb-connector-nodejs implementation.
 """
 
+from functools import lru_cache
 from typing import List, Tuple
 
-def split_sql_parts(sql: str) -> Tuple[bytes, List[int]]:
-    """
-    Find positions of positional placeholders (?) in SQL and return SQL as bytes.
-
-    Args:
-        sql: SQL statement
 
-    Returns:
-        Tuple of (sql_bytes, placeholder_byte_positions)
-        - sql_bytes: SQL encoded as UTF-8 bytes
-        - placeholder_byte_positions: List of byte positions (start, end) pairs
-    """
+@lru_cache(maxsize=256)
+def split_sql_parts(sql: str) -> Tuple[bytes, List[int]]:
     sql_bytes = sql.encode('utf-8')
+    length = len(sql_bytes)
     param_positions: List[int] = []
-
-    NORMAL = 0
-    STRING = 1
-    ESCAPE = 2
-    BACKTICK = 3
-    EOL = 4
-    COMMENT = 5
-    state = NORMAL
+    
+    state = 0  # 0=NORMAL, 1=STRING, 2=ESCAPE, 3=BACKTICK, 4=EOL, 5=COMMENT
     single_quotes = False
-
-    last_char = 0  # only used for comment detection
-
-    for i, c in enumerate(sql_bytes):
-        if state == ESCAPE:
-            # Escaped char ends escape sequence
-            state = STRING
+    last_char = 0
+    i = 0
+
+    while i < length:
+        c = sql_bytes[i]
+        
+        if state == 2:  # ESCAPE
+            state = 1
             last_char = c
+            i += 1
             continue
 
-        if state == NORMAL:
-            # Use dict lookup for clarity if desired
+        if state == 0:  # NORMAL
             if c == 63:  # '?'
                 param_positions.append(i)
                 param_positions.append(i + 1)
             elif c == 39:  # "'"
-                state = STRING
+                state = 1
                 single_quotes = True
             elif c == 34:  # '"'
-                state = STRING
+                state = 1
                 single_quotes = False
             elif c == 96:  # '`'
-                state = BACKTICK
-            elif c == 92:  # '\'
-                pass  # nothing to do in NORMAL
-            elif c == 42:  # '*'
-                if last_char == 47:  # '/*'
-                    # Check for executable comment
-                    if i + 1 < len(sql_bytes):
-                        next_c = sql_bytes[i + 1]
-                        if next_c not in (33, 77):  # '!' or 'M'
-                            state = COMMENT
-                    else:
-                        state = COMMENT
+                state = 3
+            elif c == 42 and last_char == 47:  # '/*'
+                if i + 1 < length:
+                    next_c = sql_bytes[i + 1]
+                    if next_c not in (33, 77):  # not '!' or 'M'
+                        state = 5
+                else:
+                    state = 5
             elif c == 47:  # '/'
-                if last_char == 42:  # end of comment '*/'
-                    state = NORMAL
-                elif last_char == 47:  # start of // comment
-                    state = EOL
+                if last_char == 42:  # '*/'
+                    state = 0
+                elif last_char == 47:  # '//'
+                    state = 4
             elif c == 35:  # '#'
-                state = EOL
-            elif c == 45:  # '-'
-                if last_char == 45:  # '--'
-                    state = EOL
+                state = 4
+            elif c == 45 and last_char == 45:  # '--'
+                state = 4
 
-        elif state == STRING:
+        elif state == 1:  # STRING
             if c == 92:  # '\'
-                state = ESCAPE
+                state = 2
             elif (c == 39 and single_quotes) or (c == 34 and not single_quotes):
-                state = NORMAL
+                state = 0
 
-        elif state == BACKTICK:
-            if c == 96:  # '`'
-                state = NORMAL
+        elif state == 3:  # BACKTICK
+            if c == 96:
+                state = 0
 
-        elif state == EOL:
+        elif state == 4:  # EOL
             if c == 10:  # '\n'
-                state = NORMAL
+                state = 0
 
-        elif state == COMMENT:
+        elif state == 5:  # COMMENT
             if last_char == 42 and c == 47:  # '*/'
-                state = NORMAL
+                state = 0
 
         last_char = c
+        i += 1
 
-    return sql_bytes, param_positions
+    return sql_bytes, param_positions