title: Merging two large dataframe in Pandas
body: <p>How should i merge the <code>label</code> column in dataframe <code>df</code>(8 million rows) to another dataframe <code>df2</code> (143 million rows) when the data size is that large?</p>
  <p>Basically I just want to map the <code>label</code> column to <code>df2</code>, all the data in <code>df</code> is included in <code>df2</code> except the <code>label</code> column. Is there anyway I can solve this issue instead of using <code>merge()</code>?</p>
  <p>Tried to run the code below, but it keeps running for 5 hours but has no response.</p>
  <pre><code>result = pd.merge(df,df2,on=[&quot;X&quot;, &quot;Y&quot;, &quot;Z&quot;], how='left')
  result
  </code></pre>
  <p>df</p>
  <p><a href="https://i.stack.imgur.com/oc8Z9.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/oc8Z9.png" alt="enter image description here" /></a></p>
  <p>df2</p>
  <p><a href="https://i.stack.imgur.com/LxY1k.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/LxY1k.png" alt="enter image description here" /></a></p>