<p dir="auto">We seem to have broken compatibility with fortran-interface-only BLAS libraries.  Specifically, we use <code class="notranslate">cblas_zdotc_sub</code> and <code class="notranslate">cblas_cdotc_sub</code>, which don't exist in some BLAS implementations such as CentOS 7's default <code class="notranslate">blas</code> package.  Is this something we want to work around, revert, or just live with?</p>
<p dir="auto">I'd like to propose two added functions to the <code class="notranslate">merge</code> function. I'm not sure if this needs to be in core language or somewhere like in DataFrames, but as long as <code class="notranslate">merge</code> is in core, seems reasonable to put here (though input welcome!).</p>
<p dir="auto">In particular, I'd like to propose the following two options be offered as optional keywords:</p>
<ul dir="auto">
<li><code class="notranslate">validate</code>: duplicates the functionality of <code class="notranslate">validate</code> keyword in the <code class="notranslate">pandas</code> <a href="https://pandas.pydata.org/pandas-docs/stable/generated/pandas.DataFrame.merge.html" rel="nofollow">merge</a> function. Accepts <code class="notranslate">"1:1"</code>, <code class="notranslate">"1:m"</code>, <code class="notranslate">"m:1"</code>, and <code class="notranslate">"m:m"</code>, and raises an exception if the merge is not 1 to 1, 1 to many, many to 1, or many to many (respectively).</li>
<li><code class="notranslate">indicator</code>: duplicates functionality of <code class="notranslate">indicator</code> keyword in <code class="notranslate">pandas</code> [merge] function. If <code class="notranslate">True</code>, adds column to returned object which records whether resulting row has data from <code class="notranslate">both</code> datasets, from the <code class="notranslate">left_only</code>, or the <code class="notranslate">right_only</code> (or if we'd prefer numerics for generality, 1, 2, and 3)</li>
</ul>
<p dir="auto">(Both are actually replications of behavior from <a href="https://www.stata.com/manuals13/dmerge.pdf" rel="nofollow">Stata</a>)</p>
<p dir="auto">Personally, I find these exceedingly value when working with real world data, as there's no place problems become more evident than in merges, and it gets exhausting writing code the replicates these functionalities every time I merge (especially the <code class="notranslate">indicator</code> command).</p>