how do you change a column name when the column already has data in it?
#how do you change a column name when the column already has data in it?
graceful wasp
long elkBOT
Hi @graceful wasp. I'm kapa.ai, your friendly support bot. I will try to answer your question by searching through the knowledge base. :wave:
To change a column name in Convex when the column already has data in it, you would need to perform a migration. This involves creating a new column with the new name, migrating all the data from the old column to the new one, and then deleting the old column.
Here is an example of how you can do this:
export const changeColumn = internalMutation(
async (ctx) => {
for await (const row of ctx.db.query('mytable')) {
await ctx.db.patch(row._id, {
NewColumnName: row["OldColumnName"],
"OldColumnName": undefined,
});
}
});
You can run this migration using the dashboard or npx convex run.
If you have a large table with thousands of rows, you might need to do this in batches. You can use the migration helpers for this. Here is an example:
const toNewColumnName = migration({
table: "mytable",
migrateOne: (ctx, row) => ({
NewColumnName: row.OldColumnName,
OldColumnName: undefined,
}),
});
Please note that Convex does not currently support renaming columns in a way that doesn't involve re-writing all of your documents in the table. Also, be aware that this operation might consume your bandwidth if you have a large amount of data.
For more information, you can refer to these resources:
- Discord support thread: Is there a way to rename columns in a table? (https://discord.com/channels/1019350475847499849/1174188392653783060)
- Intro to Migrations (https://stack.convex.dev/intro-to-migrations)
Note: you can ask me a follow up question by @ mentioning me again :speech_balloon:
graceful wasp
@long elk I have a table, users, and I want to change the column name to fullName. What's the code to accomplish this? Assume performance/bandwidth is not a constraint
long elkBOT
Let me check the knowledge base for you. One moment! :books:
To change the column name in your users table from name to fullName, you can use the following code:
export const changeColumnName = internalMutation(
async (ctx) => {
for await (const row of ctx.db.query('users')) {
await ctx.db.patch(row._id, {
fullName: row["name"],
"name": undefined,
});
}
});
This code creates a new column fullName and copies all the data from the name column to it. Then it sets the name column to undefined, effectively deleting it.
You can run this mutation using the dashboard or npx convex run.
Please note that this operation will rewrite all of your documents in the users table.