Join epc & pp

pipeline/fuzzy_join.py

@@ -0,0 +1,139 @@
+import re
+from concurrent.futures import ProcessPoolExecutor
+from os import cpu_count
+
+import polars as pl
+from thefuzz import fuzz
+from tqdm import tqdm
+
+_NUMBER_RE = re.compile(r'\d+')
+
+
+def fuzzy_join_on_postcode(
+    left: pl.DataFrame,
+    right: pl.DataFrame,
+    left_address_col: str,
+    right_address_col: str,
+    left_postcode_col: str,
+    right_postcode_col: str,
+    score_threshold: int = 80,
+) -> pl.DataFrame:
+    """Fuzzy join two DataFrames by matching addresses within postcode buckets.
+
+    Returns the left DataFrame with all right columns appended.
+    Unmatched rows have null right columns.
+    """
+
+    def _normalize(s: pl.Expr) -> pl.Expr:
+        return (
+            s.str.to_uppercase()
+            .str.replace_all(r'[,.\-]', ' ')
+            .str.replace_all(r'\s+', ' ')
+            .str.strip_chars()
+        )
+
+    left = left.with_columns(
+        _normalize(pl.col(left_address_col)).alias('_left_address'),
+        pl.col(left_postcode_col).str.strip_chars().str.to_uppercase().alias('_left_postcode'),
+    )
+    right = right.with_columns(
+        _normalize(pl.col(right_address_col)).alias('_right_address'),
+        pl.col(right_postcode_col).str.strip_chars().str.to_uppercase().alias('_right_postcode'),
+    )
+
+    # Deduplicate right side on normalized address + postcode so that
+    # variant spellings of the same address don't consume multiple slots.
+    right = right.unique(subset=['_right_address', '_right_postcode'], keep='first')
+
+    # Group right side by postcode for fast lookup
+    right_by_postcode: dict[str, list[tuple[int, str]]] = {}
+    for i, (postcode, address) in enumerate(
+        zip(right['_right_postcode'], right['_right_address'])
+    ):
+        if postcode is not None:
+            right_by_postcode.setdefault(postcode, []).append((i, address))
+
+    # Group left side by postcode
+    left_by_postcode: dict[str, list[tuple[int, str]]] = {}
+    for left_row, (postcode, address) in enumerate(
+        zip(left['_left_postcode'], left['_left_address'])
+    ):
+        if address is not None and postcode is not None:
+            left_by_postcode.setdefault(postcode, []).append((left_row, address))
+
+    # Build tasks for each postcode bucket
+    tasks = [
+        (left_entries, right_by_postcode[postcode], score_threshold)
+        for postcode, left_entries in left_by_postcode.items()
+        if postcode in right_by_postcode
+    ]
+
+    # Score all pairwise matches in parallel, then greedily assign from
+    # highest score downward so best pairs lock in first.
+    all_pairs: list[tuple[int, int, int]] = []  # (score, left_row, right_row)
+    with ProcessPoolExecutor(max_workers=cpu_count()) as executor:
+        for pairs in tqdm(
+            executor.map(_score_bucket, tasks, chunksize=64),
+            total=len(tasks),
+            desc='Fuzzy matching',
+        ):
+            all_pairs.extend(pairs)
+
+    # Sort descending by score so best matches are assigned first
+    all_pairs.sort(key=lambda t: (t[0], -t[1]), reverse=True)
+
+    match_indices: list[int | None] = [None] * len(left)
+    matched_left: set[int] = set()
+    matched_right: set[int] = set()
+
+    for score, left_row, right_row in all_pairs:
+        if left_row in matched_left or right_row in matched_right:
+            continue
+        match_indices[left_row] = right_row
+        matched_left.add(left_row)
+        matched_right.add(right_row)
+
+    # Select right columns (excluding internal helpers)
+    right_cols = right.select(pl.exclude('_right_address', '_right_postcode'))
+    right_matched = right_cols[
+        [i if i is not None else 0 for i in match_indices]
+    ]
+
+    # Null out unmatched rows
+    mask = pl.Series('_matched', [i is not None for i in match_indices])
+    right_matched = right_matched.with_columns(
+        pl.when(mask).then(pl.col(c)).otherwise(pl.lit(None)).alias(c)
+        for c in right_matched.columns
+    )
+
+    left_clean = left.select(pl.exclude('_left_address', '_left_postcode'))
+    return pl.concat([left_clean, right_matched], how='horizontal')
+
+
+def _numbers_compatible(a: str, b: str) -> bool:
+    """Check that numeric tokens (flat/house numbers) in the shorter set are a subset of the longer.
+
+    Returns False if one address has numbers and the other doesn't.
+    """
+    nums_a = set(_NUMBER_RE.findall(a))
+    nums_b = set(_NUMBER_RE.findall(b))
+    smaller, larger = (nums_a, nums_b) if len(nums_a) <= len(nums_b) else (nums_b, nums_a)
+    if not smaller and larger:
+        return False
+    return smaller.issubset(larger)
+
+
+def _score_bucket(
+    args: tuple[list[tuple[int, str]], list[tuple[int, str]], int],
+) -> list[tuple[int, int, int]]:
+    """Score all address pairs within a single postcode bucket."""
+    left_entries, right_entries, score_threshold = args
+    pairs = []
+    for left_row, left_address in left_entries:
+        for right_row, right_address in right_entries:
+            if not _numbers_compatible(left_address, right_address):
+                continue
+            score = fuzz.token_sort_ratio(left_address, right_address)
+            if score >= score_threshold:
+                pairs.append((score, left_row, right_row))
+    return pairs