assignment week4 Fatemeh Alinejad #51
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| const db = client.db("databaseWeek4"); | ||
| const collection = db.collection("ex1-aggregation"); |
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suggestion: since these two strings are used across the files, it's better to make them constants.
| const db = client.db("databaseWeek4"); | ||
| const collection = db.collection("ex1-aggregation"); |
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Same constant suggestion applies here too.
| const db = client.db("databaseWeek4"); | ||
| const collection = db.collection("accounts"); |
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Same constant suggestion applies here too.
| if (from.balance < amount) { | ||
| throw new Error("Insufficient balance"); | ||
| } |
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Early returns and throwing are always good if applicable :)
| const changeNumberFrom = from.account_changes.length + 1; | ||
| const changeNumberTo = to.account_changes.length + 1; |
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suggestion: using fromAccount.account_changes.length + 1 to know the next change_number is OK.
However, in real life one account may have a lot more change records. We don't really care what those changes are, we just want to know the maximum change number. Fetching all changes with the account can be expensive (since you need to transfer more bytes in the network. When you download something big from Internet, it is always slower than dowloading smaller files using the same network), and we try to only fetch the columns we need.
One solution is to have a function to get only the maximum change number (you have learned MAX sql syntax), and when you fetch the account data you don't fetch the changes column.
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