Make reconcile.py work against SQL Server / linked-server sources

reconcile.py was written against the DB2 LGDAT modules and broke four
different ways on the first GP module (sop30200):

- detect_source_from's regex handled at most a two-part name, so
  CHG.dbo.SOP30200 truncated to CHG.dbo -> "Invalid object name".
  Now matches 1-4 parts, including [bracketed] and "quoted" forms.

- Even fully qualified, that table only exists behind the GPSERVER
  linked server. Detect the module's OPENQUERY wrapper and push the
  aggregate through it, so the scan runs remotely and one row comes
  back instead of 1.6M rows crossing the link.

- OPENQUERY caps its passthrough string at 8000 chars and 291 metrics
  overran it. Split the metric list into chunks that fit and CROSS JOIN
  them back into one row; alias columns c0..cN since OPENQUERY rejects
  unnamed result columns (msg 8155). EXEC(@sql) AT has no such cap but
  needs RPC Out, which GPSERVER has disabled.

- Two dialect bugs that would hit any SQL Server source: T-SQL SUM(int)
  stays int and overflowed at 2^31 where Postgres promotes to bigint,
  and T-SQL has no LENGTH. Added Driver.sum_expression /
  length_expression with mssql overrides -- integer types cast to
  BIGINT (decimals left alone so scale isn't lost), LENGTH -> LEN.

--super-quick and --quick now run clean end to end. Full depth is
syntax-checked only; it wasn't run against the server.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

pipekit/drivers/base.py

@@ -167,6 +167,18 @@ class Driver(abc.ABC):
         """DDL to create new_table with the same columns as source_table."""
         return f"CREATE TABLE {new_table} (LIKE {source_table} INCLUDING ALL);"
 
+    # ---- reconciliation aggregates ----
+    # Used by reconcile.py to build the same aggregate on both sides of a sync.
+    # They must agree numerically across dialects, not merely parse.
+
+    def sum_expression(self, type_raw: str, expr: str) -> str:
+        """SUM over ``expr``, widened where the dialect would overflow."""
+        return f"SUM({expr})"
+
+    def length_expression(self, expr: str) -> str:
+        """Character length of ``expr``."""
+        return f"LENGTH({expr})"
+
     def build_add_column_sql(self, qualified_table: str, column: dict) -> str:
         """DDL to append one column to an existing table. ALTER can only add
         at the end — which keeps the positional load aligned as long as the

pipekit/drivers/mssql.py

@@ -209,6 +209,20 @@ class MSSQLDriver(Driver):
             return f"RTRIM({col})"
         return col
 
+    # T-SQL's SUM keeps the operand's type, so summing an int column overflows
+    # at 2^31 where Postgres would have promoted to bigint. Widen the integer
+    # types only — decimals already promote to decimal(38,s), and casting them
+    # would risk losing scale.
+    _INT_TYPES = {"int", "integer", "smallint", "tinyint", "bit"}
+
+    def sum_expression(self, type_raw: str, expr: str) -> str:
+        if _base(type_raw) in self._INT_TYPES:
+            return f"SUM(CAST({expr} AS BIGINT))"
+        return f"SUM({expr})"
+
+    def length_expression(self, expr: str) -> str:
+        return f"LEN({expr})"  # T-SQL has no LENGTH
+
     def map_type(self, type_raw: str) -> str:
         base = _base(type_raw)
         mapped = _TYPE_MAP.get(base, "text")

reconcile.py

@@ -65,6 +65,19 @@ def source_expression(drv, column: dict) -> str:
     return drv.default_expression(column["source_type"], name)
 
 
+# One name part: "quoted", [bracketed], or bare. A table reference is 1-4 of
+# them dot-joined — SQL Server's linked-server form (server.db.schema.table) is
+# the reason for 4, GP's CHG.dbo.SOP30200 the reason 2 was never enough.
+_PART = r'(?:"[^"]+"|\[[^\]]+\]|[\w#$]+)'
+_FROM_RE = re.compile(rf'FROM\s+({_PART}(?:\.{_PART}){{0,3}})', re.IGNORECASE)
+_OPENQUERY_RE = re.compile(r'OPENQUERY\s*\(\s*([\w#$]+)\s*,', re.IGNORECASE)
+
+
+def _base_name(ref: str) -> str:
+    """Last part of a dotted table reference, unquoted and lowercased."""
+    return ref.split(".")[-1].strip('"').strip("[]").lower()
+
+
 def detect_source_from(source_query: str, dest_table: str) -> str | None:
     """Best-effort: find the base source table in the module's SELECT.
 
@@ -72,18 +85,70 @@ def detect_source_from(source_query: str, dest_table: str) -> str | None:
     base name (the modules here name the dest after the source); falls back to
     the last FROM match. Returns None if nothing looks like a table.
     """
-    matches = re.findall(r'FROM\s+("?[\w#]+"?\.?"?[\w#]*"?)', source_query,
-                         flags=re.IGNORECASE)
-    matches = [m.strip() for m in matches if "." in m]
+    matches = [m.strip() for m in _FROM_RE.findall(source_query) if "." in m]
     if not matches:
         return None
-    dest_base = dest_table.split(".")[-1].strip('"').lower()
+    dest_base = _base_name(dest_table)
     for m in matches:
-        if m.split(".")[-1].strip('"').lower() == dest_base:
+        if _base_name(m) == dest_base:
             return m
     return matches[-1]
 
 
+def detect_openquery_server(source_query: str) -> str | None:
+    """Linked-server name if the module reads through ``OPENQUERY(SRV, '...')``.
+
+    The GP modules wrap their whole SELECT in OPENQUERY so the work runs on the
+    remote server. The table named inside that string (``CHG.dbo.SOP30200``)
+    does not resolve on the local connection, so reconcile has to push its
+    aggregate through the same wrapper rather than querying the table directly.
+    """
+    m = _OPENQUERY_RE.search(source_query)
+    return m.group(1) if m else None
+
+
+def build_openquery_sql(server: str, table: str, exprs: list[str], *,
+                        limit: int = 7000) -> str:
+    """Aggregate ``exprs`` over ``table`` on linked server ``server``.
+
+    Columns are aliased ``c0..cN`` because OPENQUERY rejects a passthrough
+    result set with unnamed columns (msg 8155); the aliases are positional and
+    results are still zipped by position, never by name.
+
+    OPENQUERY's passthrough string is capped at 8000 characters and a wide
+    module overruns it (sop30200: 291 metrics), so the metric list is split
+    into chunks that each fit and CROSS JOINed back into the single row the
+    caller expects. `SELECT *` over the join preserves left-to-right order, so
+    the columns still line up with the labels. Each chunk costs one extra
+    remote scan — hence chunks as large as the cap allows.
+
+    (The uncapped alternative, ``EXEC(@sql) AT server``, needs RPC Out enabled
+    on the linked server; GPSERVER has it off.)
+    """
+    overhead = len("SELECT  FROM ") + len(table)
+    chunks: list[list[str]] = []
+    cur: list[str] = []
+    cur_len = overhead
+    for i, e in enumerate(exprs):
+        piece = f"{e} AS c{i}"
+        add = len(piece) + (2 if cur else 0)
+        if cur and cur_len + add > limit:
+            chunks.append(cur)
+            cur, cur_len = [], overhead
+            add = len(piece)
+        cur.append(piece)
+        cur_len += add
+    if cur:
+        chunks.append(cur)
+
+    parts = []
+    for n, pieces in enumerate(chunks):
+        inner = f"SELECT {', '.join(pieces)} FROM {table}"
+        escaped = inner.replace("'", "''")
+        parts.append(f"OPENQUERY({server}, '{escaped}') q{n}")
+    return "SELECT * FROM " + "\n  CROSS JOIN ".join(parts)
+
+
 def build_metrics(columns, key_names, drv, *, source: bool, quick: bool,
                   super_quick: bool = False):
     """Return (list of (label, kind) metric descriptors, list of SQL exprs).
@@ -118,11 +183,13 @@ def build_metrics(columns, key_names, drv, *, source: bool, quick: bool,
             e = drv.quote_identifier(c["dest_name"])
         name = c["dest_name"]
 
+        col_type = c["source_type"] if source else c["dest_type"]
+
         if kind == "numeric":
             labels.append((f"{name}: count", "int"))
             exprs.append(f"COUNT({e})")
             labels.append((f"{name}: sum", "num"))
-            exprs.append(f"SUM({e})")
+            exprs.append(drv.sum_expression(col_type, e))
             if not quick:
                 labels.append((f"{name}: min", "str"))
                 exprs.append(f"MIN({e})")
@@ -141,7 +208,7 @@ def build_metrics(columns, key_names, drv, *, source: bool, quick: bool,
             exprs.append(f"COUNT({e})")
             if not quick:
                 labels.append((f"{name}: len_sum", "int"))
-                exprs.append(f"SUM(LENGTH({e}))")
+                exprs.append(drv.sum_expression("int", drv.length_expression(e)))
 
     return labels, exprs
 
@@ -216,8 +283,19 @@ def main() -> int:
     src_sql = "SELECT\n  " + "\n , ".join(src_exprs) + f"\nFROM {source_from}"
     dst_sql = "SELECT\n  " + "\n , ".join(dst_exprs) + f"\nFROM {m['dest_table']}"
 
+    # An explicit --source-from is taken verbatim (the caller may already have
+    # written their own OPENQUERY). Otherwise, if the module reads through a
+    # linked server, push the aggregate down the same way: computing it here
+    # would drag every row across the link, and the inner table name does not
+    # resolve locally at all.
+    oq_server = None if args.source_from else detect_openquery_server(m["source_query"])
+    if oq_server:
+        src_sql = build_openquery_sql(oq_server, source_from, src_exprs)
+
     print(f"module {m['name']}  (id {m['id']})")
-    print(f"  source {src_conn['name']}  FROM {source_from}")
+    src_label = (f"OPENQUERY({oq_server}) -> {source_from}" if oq_server
+                 else source_from)
+    print(f"  source {src_conn['name']}  FROM {src_label}")
     print(f"  dest   {dst_conn['name']}  FROM {m['dest_table']}")
     mode = ("  [super-quick]" if args.super_quick
             else "  [quick]" if args.quick else "")