Is there a way to resize an account's data field?

Question

I am pretty sure I remember reading somewhere that once the space is allocated for an account, it cannot be changed. Is this true? If so, can you delete the account and re-initialize it with a different amount of space? Are there any other ways of handling this?

As a specific use case: What if a string was set in storage on some program PDA account and someone wanted to update that string with something larger? What would that process look like? Is it possible?

Answer 1

From the anchor lang 25.0 docs, they have implemented the realloc constraint to give you access to the new functionality of resizing accounts. This functionality is particularly relevant for PDAs which can only be inited with 10kb of space and is limited to a 10kb increase in size each block (or maybe it's per transaction?).

• realloc = sets the new space in bytes
• realloc::payer = points to an account with Sol to pay for the extra space
• realloc::zero = indicates whether you want the data in the account to be zeroed out (basically refresh and delete the entire account). In most cases you may not want this.

Anchor encourages using their constraints over the built in AccountInfo method because it's possible you might over allocate space and mess with other accounts, check the docs for more deets.

#[derive(Accounts)]
pub struct Example {
    #[account(mut)]
    pub payer: Signer<'info>,
    #[account(
        mut,
        seeds = [b"example"],
        bump,
        realloc = 8 + std::mem::size_of::() + 100,
        realloc::payer = payer,
        realloc::zero = false,
    )]
    pub acc: Account<'info, MyType>,
    pub system_program: Program<'info, System>,
}