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Re-implement division for numeric values using the traditional "schoolbook"
algorithm. This is a good deal slower than our old roundoff-error-prone code for long inputs, so we keep the old code for use in the transcendental functions, where everything is approximate anyway. Also create a user-accessible function div(numeric, numeric) to provide access to the exact result of trunc(x/y) --- since the regular numeric / operator will round off its result, simply computing that expression in SQL doesn't reliably give the desired answer. This fixes bug #3387 and various related corner cases, and improves the usefulness of PG for high-precision integer arithmetic.
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‎doc/src/sgml/func.sgml

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<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.426 2008/04/04 16:57:21 momjian Exp $ -->
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<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.427 2008/04/04 18:45:36 tgl Exp $ -->
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<chapter id="functions">
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<title>Functions and Operators</title>
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<indexterm>
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<primary>degrees</primary>
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</indexterm>
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<indexterm>
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<primary>div</primary>
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</indexterm>
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<indexterm>
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<primary>exp</primary>
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</indexterm>
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<entry><literal>28.6478897565412</literal></entry>
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</row>
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<row>
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<entry><literal><function>div</function>(<parameter>y</parameter> <type>numeric</>,
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<parameter>x</parameter> <type>numeric</>)</literal></entry>
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<entry><type>numeric</></entry>
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<entry>integer quotient of <parameter>y</parameter>/<parameter>x</parameter></entry>
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<entry><literal>div(9,4)</literal></entry>
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<entry><literal>2</literal></entry>
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</row>
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<row>
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<entry><literal><function>exp</function>(<type>dp</type> or <type>numeric</type>)</literal></entry>
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<entry>(same as input)</entry>

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