问题
Say you have three prepared NpgsqlCommands. Because they must be executed separatedly. But sometimes two or all three must be executed at once (well, one after the other).
Is there a way to batch and reuse these previously prepared commands using a single roundtrip to the server? (goal is to minimize latency)
Now I use a fourth command and semicolon separate a copy of the original three commands, and prepare this -- but I assume this will use more resources at the server, and more SQL parsing at the npgsql client.
回答1:
Npgsql supports batching through including several statements in your CommandText, separated by semicolons. These are executed in a single network roundtrip, and can also be prepared:
cmd.CommandText = "SELECT ...; UPDATE ...";
cmd.Prepare();
Internally, Npgsql splits such commands on semicolons and prepares each statement separately (PostgreSQL does not actually recognize batches, only individual statements). In addition, Npgsql manages prepared statements on a statement-by-statement level, and knows to reuse already-existing statements. This means that if you prepare two commands which contain the same statements, those statements will share the same server-side prepared statement resource.
来源：https://stackoverflow.com/questions/53262323/batching-separate-prepared-npgsql-commands