82 lines
3.0 KiB
Python
82 lines
3.0 KiB
Python
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"""PostgreSQL DB-API bridge for legacy '?' SQL (optional, requires psycopg[binary]).
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No automatic conversion of existing SQLite files is attempted. Production migration
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requires a tested one-time data migration and reconciliation.
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"""
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from __future__ import annotations
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import re
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from contextlib import contextmanager
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def placeholders(sql: str) -> str:
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"""Translate SQLite positional placeholders outside SQL quoted strings."""
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out=[];quote=None;i=0
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while i<len(sql):
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ch=sql[i]
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if quote:
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out.append(ch)
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if ch==quote:
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if i+1<len(sql) and sql[i+1]==quote:
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out.append(sql[i+1]);i+=1
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else:quote=None
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elif ch in ("'",'"'):
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quote=ch;out.append(ch)
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elif ch=='?':out.append('%s')
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else:out.append(ch)
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i+=1
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return ''.join(out)
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def normalize(sql: str) -> str:
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sql=sql.strip()
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if re.match(r'^INSERT\s+OR\s+IGNORE\s+INTO\b',sql,re.I):
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sql=re.sub(r'^INSERT\s+OR\s+IGNORE\s+INTO\b','INSERT INTO',sql,flags=re.I)
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sql=sql.rstrip(';')+' ON CONFLICT DO NOTHING'
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return placeholders(sql)
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class PGConnection:
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def __init__(self,dsn):
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import psycopg
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from psycopg.rows import dict_row
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self.connection=psycopg.connect(dsn,row_factory=dict_row,connect_timeout=5)
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self.total_changes=0
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def execute(self,sql,params=()):
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stripped=sql.strip()
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if stripped.upper().startswith('PRAGMA TABLE_INFO('):
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table=stripped.split('(',1)[1].split(')',1)[0].strip().strip('"\'')
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if not re.fullmatch(r'[A-Za-z_][A-Za-z0-9_]*',table):raise ValueError('Invalid table name')
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return self.connection.execute('SELECT column_name AS name FROM information_schema.columns WHERE table_schema=current_schema() AND table_name=%s',(table,))
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if stripped.upper()=='BEGIN IMMEDIATE':
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# Conservative transaction-wide lock while porting SQLite queue semantics.
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# Replace with per-site advisory locks before large multi-worker scale.
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return self.connection.execute('SELECT pg_advisory_xact_lock(823947231)')
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if stripped.upper().startswith('PRAGMA '):
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return _EmptyResult()
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cursor=self.connection.execute(normalize(sql),params)
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if cursor.rowcount and cursor.rowcount>0 and stripped.split(None,1)[0].upper() in ('UPDATE','INSERT','DELETE'):
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self.total_changes+=cursor.rowcount
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return cursor
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def executescript(self,script):
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# Schema migrations contain only simple DDL and SQLite PRAGMA statements.
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for statement in script.split(';'):
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if statement.strip():self.execute(statement)
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def __enter__(self):return self
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def __exit__(self,typ,val,tb):
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try:
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if typ:self.connection.rollback()
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else:self.connection.commit()
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finally:self.connection.close()
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return False
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class _EmptyResult:
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rowcount=0
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def fetchone(self):return None
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def fetchall(self):return []
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def connect(dsn):return PGConnection(dsn)
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