<p>OSM tags are very similar to JSON fields. So I think that it will be great to have JSON data representation in database. Postgresql allows indexes on JSON fields and store this data more effectively than plain text arrays.<br>
I made some tests on my dataset (USA East Coast) and have this numbers:</p>
<table>
<thead>
<tr>
<th>method</th>
<th align="right">tags size in _ways</th>
<th align="right">tags size in _rels</th>
</tr>
</thead>
<tbody>
<tr>
<td>array</td>
<td align="right">4422 mb</td>
<td align="right">36 mb</td>
</tr>
<tr>
<td>jsonb</td>
<td align="right">3805 mb</td>
<td align="right">32 mb</td>
</tr></tbody></table>

<hr>

<h4>You can view, comment on, or merge this pull request online at:</h4>
<p>  <a href='https://github.com/openstreetmap/osm2pgsql/pull/738'>https://github.com/openstreetmap/osm2pgsql/pull/738</a></p>

<h4>Commit Summary</h4>
<ul>
  <li>JSONB column for tags inside the pgsql middle.</li>
</ul>

<h4>File Changes</h4>
<ul>
  <li>
    <strong>M</strong>
    <a href="https://github.com/openstreetmap/osm2pgsql/pull/738/files#diff-0">middle-pgsql.cpp</a>
    (17)
  </li>
</ul>

<h4>Patch Links:</h4>
<ul>
  <li><a href='https://github.com/openstreetmap/osm2pgsql/pull/738.patch'>https://github.com/openstreetmap/osm2pgsql/pull/738.patch</a></li>
  <li><a href='https://github.com/openstreetmap/osm2pgsql/pull/738.diff'>https://github.com/openstreetmap/osm2pgsql/pull/738.diff</a></li>
</ul>

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