Batch Insert Optimization for MSSQL

[jpgilchrist]

The batchInsert functionality is incredibly inefficient. Shouldn't it utilize the underlying driver's utilities for batch processing? I.e., for mssql it should use

https://github.com/tediousjs/node-mssql#bulk-table-options-callback

const sql = db.client.driver;

  let connection = await db.client.acquireConnection();

  const table = new sql.Table("table");

  table.columns.add("col1", sql.Int, { nullable: false });
  table.columns.add("col2", sql.VarChar(255), {
    nullable: true
  });
  items.forEach(item => {
    table.rows.add(item.col1, item.col2 );
  });
  await new Promise((resolve, reject) => {
    const request = new sql.Request(connection);
    request.bulk(table, (err, result) => {
      console.log("bulk table", err, result);
      if (err) {
        return reject(err);
      }
      return resolve(result);
    });
  });

[elhigu]

IMO batch insert should not even exist in knex level, since it iis more of a helper than a single query that is built.

Anyways if this kind of optimization is implemented to mssql dialect with good integration tests that it works the same way with other drivers I don't have any reason why not to accept PR for this (if it doesn't complicate any other parts in knex).