Question

What’s the most efficient way to cycle through all entries in a table and replace all instances of a string with another.

For instance, I’ve got some legacy bb code that I want to replace…

Replace: [img]/images/emoticons/happy.png[/img] or <img src="/images/emoticons/happy.png">

With: :)

Answer 1

The quickest way would be to let the database do all the work:

connection.execute(%q{
    update your_table
    set your_column = replace(
        replace(
            your_column,
            '<img src="/images/emoticons/happy.png">',
            ':)'
        ),
        '[img]/images/emoticons/happy.png[/img]',
        ':)'
    )
})

If your source or target strings contain quotes (or if you’re not writing them by hand), then use connection.quote:

from1 = connection.quote('<img src="/images/emoticons/happy.png">')
from2 = connection.quote('[img]/images/emoticons/happy.png[/img]')
to    = connection.quote(':)')
connection.execute(%Q{
    update your_table
    set your_column = replace(replace(your_column, #{from1}, #{to}), #{from2}, #{to}))
})