services/horizon/internal/db2/history: Use FastBatchInsertBuilder to insert ledgers into the history_ledgers

[tamirms]

PR Checklist

PR Structure

• This PR has reasonably narrow scope (if not, break it down into smaller PRs).
• This PR avoids mixing refactoring changes with feature changes (split into two PRs
  otherwise).
• This PR's title starts with name of package that is most changed in the PR, ex.
  services/friendbot, or all or doc if the changes are broad or impact many
  packages.

Thoroughness

• This PR adds tests for the most critical parts of the new functionality or fixes.
• I've updated any docs (developer docs, .md
  files, etc... affected by this change). Take a look in the docs folder for a given service,
  like this one.

Release planning

• I've updated the relevant CHANGELOG (here for Horizon) if
  needed with deprecations, added features, breaking changes, and DB schema changes.
• I've decided if this PR requires a new major/minor version according to
  semver, or if it's mainly a patch change. The PR is targeted at the next
  release branch if it's not a patch change.

What

In #4916 we introduced a FastBatchInsertBuilder which can be used to quickly insert a large amount of rows into Postgres via the COPY command. In this PR, we use FastBatchInsertBuilder to insert ledgers into the history_ledgers table.

Why

As a part of #4908 , we want to update all the code which inserts data into the history tables to use the FastBatchInsertBuilder.

Known limitations

[N/A]

[Shaptic]

👏 nice

just one design comment below ⬇️

[Shaptic]

almost sounds like this could be generalized into a tableBatchInsertBuilder and reused?

[tamirms]

db.FastBatchInsertBuilder is the component which could be used by multiple tables. ledgerBatchInsertBuilder has an Add() function which is specific to inserting ledgers. For other tables the Add() function would take different parameters

[Shaptic]

Ah sure, got it.

I think I was just thrown off by the fact that you have var table string as a separate variable that you explicitly assigned to "history_ledgers"; I'm seeing now that it's more of a quirk of not being able to assign in within the struct, e.g. how you can do something like

class ledgerBatchInsertBuilder {
  builder: db.FastBatchInsertBuilder;
  table: string = "history_ledgers";

  // constructors, etc...
}

in JS.