Open or replace a dynamic PostgreSQL/MySQL/MongoDB connection.

Execute a MongoDB command query. Use MongoDB command syntax, not Mongo shell JavaScript. Do not generate db.collection.find(...) or db.users.aggregate(...). Instead generate command JSON such as {"find":"users","filter":{"active":true},"limit":10}. For aggregate, include "cursor": {}, for example {"aggregate":"orders","pipeline":[{"$match":{"status":"paid"}}],"cursor":{}}. Use query when providing a string; it must be valid Extended JSON. Use $oid/$date Extended JSON for BSON values. In --readOnly mode, write/unknown commands are rejected, and aggregate with $out/$merge is treated as write.

Execute one PostgreSQL or MySQL SQL statement with optional positional parameters. Generate normal SQL, not MongoDB syntax. Use params instead of interpolating values into sql. For PostgreSQL placeholders use $1, $2, ...; for MySQL placeholders use ?. In --readOnly mode, write/transaction/unknown SQL is rejected.

Begin a transaction for a connection.

Commit the current transaction for a connection.

Rollback the current transaction for a connection.

Close one connection, or the latest connection if no id is supplied.