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diff --git a/doc/src/sgml/ref/create_aggregate.sgml b/doc/src/sgml/ref/create_aggregate.sgml new file mode 100644 index 00000000000..b52c002fd63 --- /dev/null +++ b/doc/src/sgml/ref/create_aggregate.sgml @@ -0,0 +1,300 @@ +<REFENTRY ID="SQL-CREATEAGGREGATE-1"> + <REFMETA> + <REFENTRYTITLE> + CREATE AGGREGATE + </REFENTRYTITLE> + <REFMISCINFO>SQL - Language Statements</REFMISCINFO> + </REFMETA> + +<comment>This entry needs a lot of work, especially some +usefully complex examples. Since I don't yet understand it, I +haven't done this.</comment> + + <REFNAMEDIV> + <REFNAME> + CREATE AGGREGATE + </REFNAME> + <REFPURPOSE> + Defines a new aggregate function + </REFPURPOSE> + <REFSYNOPSISDIV> + <REFSYNOPSISDIVINFO> + <DATE>1998-04-15</DATE> + </REFSYNOPSISDIVINFO> + <SYNOPSIS> + CREATE AGGREGATE <REPLACEABLE CLASS="PARAMETER">name</REPLACEABLE> [AS] + ([ SFUNC1 = <REPLACEABLE CLASS="PARAMETER">state_transition_function1</REPLACEABLE> + , BASETYPE = <REPLACEABLE CLASS="PARAMETER">data_type</REPLACEABLE> + , STYPE1 = <REPLACEABLE CLASS="PARAMETER">sfunc1_return_type</REPLACEABLE> ] + [, SFUNC2 = <REPLACEABLE CLASS="PARAMETER">state_transition_function2</REPLACEABLE> + , STYPE2 = <REPLACEABLE CLASS="PARAMETER">sfunc2_return_type</REPLACEABLE> ] + [, FINALFUNC = <REPLACEABLE CLASS="PARAMETER">final_function</REPLACEABLE> ] + [, INITCOND1 = <REPLACEABLE CLASS="PARAMETER">initial_condition1</REPLACEABLE> ] + [, INITCOND2 = <REPLACEABLE CLASS="PARAMETER">initial_condition2</REPLACEABLE> ] + ) + </SYNOPSIS> + + <REFSECT2 ID="R2-SQL-CREATEAGGREGATE-1"> + <REFSECT2INFO> + <DATE>1998-04-15</DATE> + </REFSECT2INFO> + <TITLE> + Inputs + </TITLE> + <variablelist> + <varlistentry> + <term></term> + <listitem> + <PARA> + <VARIABLELIST> + <VARLISTENTRY> + <TERM> + <REPLACEABLE CLASS="PARAMETER">name</REPLACEABLE> + </TERM> + <LISTITEM> + <para> + The name of an aggregate function to create. + </para> + </LISTITEM> + </varlistentry> + <varlistentry> + <term> + <REPLACEABLE CLASS="PARAMETER">state_transition_function1</REPLACEABLE> + </term> + <listitem> + <para> + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <REPLACEABLE CLASS="PARAMETER">data_type</REPLACEABLE> + </term> + <listitem> + <para> + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <REPLACEABLE CLASS="PARAMETER">sfunc1_return_type</REPLACEABLE> + </term> + <listitem> + <para> + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <REPLACEABLE CLASS="PARAMETER">state-transition_function2</REPLACEABLE> + </term> + <listitem> + <para> + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <REPLACEABLE CLASS="PARAMETER">sfunc2_return_type</REPLACEABLE> + </term> + <listitem> + <para> + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <REPLACEABLE CLASS="PARAMETER">final_function</REPLACEABLE> + </term> + <listitem> + <para> + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <REPLACEABLE CLASS="PARAMETER">initial_condition1</REPLACEABLE> + </term> + <listitem> + <para> + </para> + </listitem> + </varlistentry> + <varlistentry> + <term> + <REPLACEABLE CLASS="PARAMETER">initial_condition2</REPLACEABLE> + </term> + <listitem> + <para> + </para> + </listitem> + </varlistentry> + </variablelist> + </PARA> + </listitem> + </varlistentry> + </variablelist> + </REFSECT2> + + <REFSECT2 ID="R2-SQL-CREATEAGGREGATE-2"> + <REFSECT2INFO> + <DATE>1998-04-15</DATE> + </REFSECT2INFO> + <TITLE> + Outputs + </TITLE> + <PARA> + </PARA> + <VARIABLELIST> + <VARLISTENTRY> + <TERM> + </TERM> + <LISTITEM> + <PARA> + <VARIABLELIST> + <VARLISTENTRY> + <TERM> + <ReturnValue>CREATE</ReturnValue> + </TERM> + <LISTITEM> + <PARA> + Message returned if the command completes successfully. + </PARA> + </LISTITEM> + </VARLISTENTRY> + </VARIABLELIST> + </LISTITEM> + </VARLISTENTRY> + </VARIABLELIST> + + </REFSECT2> + </REFSYNOPSISDIV> + + <REFSECT1 ID="R1-SQL-CREATEAGGREGATE-1"> + <REFSECT1INFO> + <DATE>1998-04-15</DATE> + </REFSECT1INFO> + <TITLE> + Description + </TITLE> + <PARA> + An aggregate function can use up to three functions, two + state transition functions, X1 and X2: + X1( internal-state1, next-data_item ) ---> next-internal-state1 + X2( internal-state2 ) ---> next-internal-state2 + and a final calculation function, F: + F(internal-state1, internal-state2) ---> aggregate-value + These functions are required to have the following properties: + <itemizedlist> + <listitem> + <para> + The arguments to state-transition-function-1 must + be (stype1,basetype), and its return value must be + stype1. + </para> + </listitem> + <listitem> + <para> + The argument and return value of state-transition- + function-2 must be stype2. + </para> + </listitem> + <listitem> + <para> + The arguments to the final-calculation-function + must be (stype1,stype2), and its return value must + be a POSTGRES base type (not necessarily the same + as basetype. + </para> + </listitem> + <listitem> + <para> + The final-calculation-function should be specified + if and only if both state-transition functions are + specified. + </para + </listitem> + </itemizedlist> + </PARA> + <para> + Note that it is possible to specify aggregate functions + that have varying combinations of state and final functions. + For example, the "count" aggregate requires sfunc2 + (an incrementing function) but not sfunc1 or finalfunc, + whereas the "sum" aggregate requires sfunc1 (an addition + function) but not sfunc2 or finalfunc and the "average" + aggregate requires both of the above state functions as + well as a finalfunc (a division function) to produce its + answer. In any case, at least one state function must be + defined, and any sfunc2 must have a corresponding initcond2. + </para> + <para> + Aggregates also require two initial conditions, one for + each transition function. These are specified and stored + in the database as fields of type text. + </para> + + <REFSECT2 ID="R2-SQL-CREATEAGGREGATE-3"> + <REFSECT2INFO> + <DATE>1998-04-15</DATE> + </REFSECT2INFO> + <TITLE> + Notes + </TITLE> + <PARA> + CREATE AGGREGATE function is a PostgreSQL language extension. + </PARA> + + <para> + Refer to DROP AGGREGATE function to drop aggregate functions. + </para> + </REFSECT2> + + <REFSECT1 ID="R1-SQL-CREATEAGGREGATE-2"> + <TITLE> + Usage + </TITLE> + <PARA> + </PARA> + <ProgramListing> + </ProgramListing> + + + </REFSECT1> + + <REFSECT1 ID="R1-SQL-CREATEAGGREGATE-3"> + <TITLE> + Compatibility + </TITLE> + <PARA> + </PARA> + + <REFSECT2 ID="R2-SQL-CREATEAGGREGATE-4"> + <REFSECT2INFO> +<DATE>1998-04-15</DATE> + </REFSECT2INFO> + <TITLE> + SQL92 + </TITLE> + <PARA> + There is no CREATE AGGREGATE function on SQL92. + </PARA> + +</REFENTRY> + +<!-- Keep this comment at the end of the file +Local variables: +mode: sgml +sgml-omittag:t +sgml-shorttag:t +sgml-minimize-attributes:nil +sgml-always-quote-attributes:t +sgml-indent-step:1 +sgml-indent-data:t +sgml-parent-document:nil +sgml-default-dtd-file:"../reference.ced" +sgml-exposed-tags:nil +sgml-local-catalogs:"/usr/lib/sgml/catalog" +sgml-local-ecat-files:nil +End: +--> |