refactor(exec): extract table scans into exec/scan.nim

src/barabadb/query/exec/scan.nim

@@ -0,0 +1,71 @@
+## Table scans — full scans and point reads against the LSM store.
+##
+## Extracted from `executor.nim` (Task 8 of the executor split).
+import std/strutils
+import std/tables
+import ../../storage/lsm
+import types
+import values
+import helpers
+import rls
+
+# ----------------------------------------------------------------------
+# Table scan and storage
+# ----------------------------------------------------------------------
+
+proc execScan*(ctx: ExecutionContext, table: string): seq[Row] =
+  result = @[]
+  # Check CTE tables first
+  if table in ctx.cteTables:
+    return ctx.cteTables[table]
+  let prefix = table & "."
+  for (key, value) in ctx.db.scanAll():
+    if not key.startsWith(prefix): continue
+    let rest = key[prefix.len..^1]
+    var row: Row
+    row["$key"] = rest
+    let valStr = cast[string](value)
+    row["$value"] = valStr
+    # Also parse individual columns
+    for k, v in parseRowData(valStr):
+      row[k] = v
+    # Extract PK value from key
+    let eqPos = rest.find('=')
+    if eqPos >= 0:
+      row[rest[0..<eqPos]] = rest[eqPos+1..^1]
+    # RLS filter
+    if passesPolicy(ctx, table, "SELECT", row):
+      # Inject qualified columns from outerRow for correlated subqueries
+      if ctx.outerRow.len > 0:
+        var outerTables: seq[string] = @[]
+        # Try to infer outer table from qualified refs already in outerRow keys
+        for k in ctx.outerRow.keys:
+          if k.contains('.') and not k.startsWith('$'):
+            let tbl = k.split('.')[0]
+            if tbl notin outerTables: outerTables.add(tbl)
+        # If no qualified keys found, scan subquery plan for correlated refs
+        if outerTables.len == 0 and ctx.subqueryPlan != nil:
+          collectCorrelatedTablesFromPlan(ctx.subqueryPlan, outerTables)
+        # Inject qualified columns
+        for k, v in ctx.outerRow:
+          if k.startsWith('$'): continue
+          if k.contains('.'): continue  # already qualified
+          for tbl in outerTables:
+            row[tbl & "." & k] = v
+      result.add(row)
+
+proc execPointRead*(ctx: ExecutionContext, table: string, key: string): seq[Row] =
+  let fullKey = table & "." & key
+  let (found, val) = ctx.db.get(fullKey)
+  if found:
+    var row: Row
+    row["$key"] = key
+    let valStr = cast[string](val)
+    row["$value"] = valStr
+    for k, v in parseRowData(valStr):
+      row[k] = v
+    let eqPos = key.find('=')
+    if eqPos >= 0:
+      row[key[0..<eqPos]] = key[eqPos+1..^1]
+    return @[row]
+  return @[]