Limiting number of items in gatsby-plugin-feed

The internals for gatsby-plugin-feed seem to indicate that we can set a limit on the number of posts that show up in the feed:

{
  // Create a default RSS feed. Others may be added by using the format below.
  feeds: [
    {
      query: `
      {
        allMarkdownRemark(
          limit: 1000,
          sort: {
            order: DESC,
            fields: [frontmatter___date]
          }
        ) {
          edges {
            node {
              frontmatter {
                title
                date
              }
              fields {
                slug
              }
              excerpt
              html
            }
          }
        }
      }
    `,
    ...
  ]
}

When I try to change limit to 10 in my own definition within gatsby-config.js, it seems to have no effect. Is there a standard way to limit the number of items in the RSS feed so that I don't have 250+ posts in there?

Solution

@AlbertSkibinski's documentation link in his comment helped me to realize that the RSS feed is only generated on gatsby build. I was making changes and trying to run gatsby develop, which had no effect on the output that I was examining in the public folder.

I am not a huge fan of overwriting default values that don't need to be overridden, so I pieced together my own config code by importing the defaults from gatsby-plugin-feed/internals:

const gatsbyFeedOpts = require('gatsby-plugin-feed/internals')

// Copy and replace limit in default options
let feedOpts = gatsbyFeedOpts.defaultOptions
feedOpts.feeds[0].query = feedOpts.feeds[0].query.replace(
  'limit: 1000',
  'limit: 10'
)

module.exports = {
  siteMetadata: {
    // Excluded for brevity
  },
  plugins: [
    // Other plugins excluded for brevity
    {
      resolve: `gatsby-plugin-feed`,
      options: feedOpts,
    },
  ],
}

It's interesting to note that even though the documentation says we need to implement a serialize method within the feed config, it wasn't included in the imported defaults that I'm using here. This could cause problems in future versions of gatsby-plugin-feed, but it works fine with the version I'm currently using (2.4.1).