reduce from 3 to 2 packages

src/nominatim_db/db/utils.py

@@ -0,0 +1,129 @@
+# SPDX-License-Identifier: GPL-3.0-or-later
+#
+# This file is part of Nominatim. (https://nominatim.org)
+#
+# Copyright (C) 2024 by the Nominatim developer community.
+# For a full list of authors see the git log.
+"""
+Helper functions for handling DB accesses.
+"""
+from typing import IO, Optional, Union, Any, Iterable
+import subprocess
+import logging
+import gzip
+import io
+from pathlib import Path
+
+from .connection import get_pg_env, Cursor
+from ..errors import UsageError
+
+LOG = logging.getLogger()
+
+def _pipe_to_proc(proc: 'subprocess.Popen[bytes]',
+                  fdesc: Union[IO[bytes], gzip.GzipFile]) -> int:
+    assert proc.stdin is not None
+    chunk = fdesc.read(2048)
+    while chunk and proc.poll() is None:
+        try:
+            proc.stdin.write(chunk)
+        except BrokenPipeError as exc:
+            raise UsageError("Failed to execute SQL file.") from exc
+        chunk = fdesc.read(2048)
+
+    return len(chunk)
+
+def execute_file(dsn: str, fname: Path,
+                 ignore_errors: bool = False,
+                 pre_code: Optional[str] = None,
+                 post_code: Optional[str] = None) -> None:
+    """ Read an SQL file and run its contents against the given database
+        using psql. Use `pre_code` and `post_code` to run extra commands
+        before or after executing the file. The commands are run within the
+        same session, so they may be used to wrap the file execution in a
+        transaction.
+    """
+    cmd = ['psql']
+    if not ignore_errors:
+        cmd.extend(('-v', 'ON_ERROR_STOP=1'))
+    if not LOG.isEnabledFor(logging.INFO):
+        cmd.append('--quiet')
+
+    with subprocess.Popen(cmd, env=get_pg_env(dsn), stdin=subprocess.PIPE) as proc:
+        assert proc.stdin is not None
+        try:
+            if not LOG.isEnabledFor(logging.INFO):
+                proc.stdin.write('set client_min_messages to WARNING;'.encode('utf-8'))
+
+            if pre_code:
+                proc.stdin.write((pre_code + ';').encode('utf-8'))
+
+            if fname.suffix == '.gz':
+                with gzip.open(str(fname), 'rb') as fdesc:
+                    remain = _pipe_to_proc(proc, fdesc)
+            else:
+                with fname.open('rb') as fdesc:
+                    remain = _pipe_to_proc(proc, fdesc)
+
+            if remain == 0 and post_code:
+                proc.stdin.write((';' + post_code).encode('utf-8'))
+        finally:
+            proc.stdin.close()
+            ret = proc.wait()
+
+    if ret != 0 or remain > 0:
+        raise UsageError("Failed to execute SQL file.")
+
+
+# List of characters that need to be quoted for the copy command.
+_SQL_TRANSLATION = {ord('\\'): '\\\\',
+                    ord('\t'): '\\t',
+                    ord('\n'): '\\n'}
+
+
+class CopyBuffer:
+    """ Data collector for the copy_from command.
+    """
+
+    def __init__(self) -> None:
+        self.buffer = io.StringIO()
+
+
+    def __enter__(self) -> 'CopyBuffer':
+        return self
+
+
+    def size(self) -> int:
+        """ Return the number of bytes the buffer currently contains.
+        """
+        return self.buffer.tell()
+
+    def __exit__(self, exc_type: Any, exc_value: Any, traceback: Any) -> None:
+        if self.buffer is not None:
+            self.buffer.close()
+
+
+    def add(self, *data: Any) -> None:
+        """ Add another row of data to the copy buffer.
+        """
+        first = True
+        for column in data:
+            if first:
+                first = False
+            else:
+                self.buffer.write('\t')
+            if column is None:
+                self.buffer.write('\\N')
+            else:
+                self.buffer.write(str(column).translate(_SQL_TRANSLATION))
+        self.buffer.write('\n')
+
+
+    def copy_out(self, cur: Cursor, table: str, columns: Optional[Iterable[str]] = None) -> None:
+        """ Copy all collected data into the given table.
+
+            The buffer is empty and reusable after this operation.
+        """
+        if self.buffer.tell() > 0:
+            self.buffer.seek(0)
+            cur.copy_from(self.buffer, table, columns=columns)
+            self.buffer = io.StringIO()