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Add SQL Standard WITH ORDINALITY support for UNNEST (and any other SRF)
Author: Andrew Gierth, David Fetter Reviewers: Dean Rasheed, Jeevan Chalke, Stephen Frost
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‎doc/src/sgml/func.sgml

Lines changed: 43 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -13278,14 +13278,56 @@ select $1[i][j]
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generate_subscripts($1,2) g2(j);
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$$ LANGUAGE sql IMMUTABLE;
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CREATE FUNCTION
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postgres=# SELECT * FROM unnest2(ARRAY[[1,2],[3,4]]);
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SELECT * FROM unnest2(ARRAY[[1,2],[3,4]]);
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unnest2
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---------
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1
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2
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3
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4
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(4 rows)
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</programlisting>
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</para>
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<indexterm>
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<primary>ordinality</primary>
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</indexterm>
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<para>
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When a function in the <literal>FROM</literal> clause is suffixed by
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<literal>WITH ORDINALITY</literal>, a <type>bigint</type> column is appended
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to the output which starts from 1 and increments by 1 for each row of the
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function's output. This is most useful in the case of set returning functions
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such as UNNEST(). This functionality is available for functions returning
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composite types or using <literal>OUT</literal> parameters, but not when using
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a function returning <literal>RECORD</literal> with an explicit column
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definition list.
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<programlisting>
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-- set returning function WITH ORDINALITY
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SELECT * FROM pg_ls_dir('.') WITH ORDINALITY AS t(ls,n);
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ls | n
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-----------------+----
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pg_serial | 1
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pg_twophase | 2
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postmaster.opts | 3
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pg_notify | 4
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postgresql.conf | 5
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pg_tblspc | 6
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logfile | 7
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base | 8
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postmaster.pid | 9
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pg_ident.conf | 10
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global | 11
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pg_clog | 12
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pg_snapshots | 13
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pg_multixact | 14
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PG_VERSION | 15
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pg_xlog | 16
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pg_hba.conf | 17
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pg_stat_tmp | 18
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pg_subtrans | 19
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(19 rows)
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</programlisting>
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</para>
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‎doc/src/sgml/ref/select.sgml

Lines changed: 35 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -52,7 +52,8 @@ SELECT [ ALL | DISTINCT [ ON ( <replaceable class="parameter">expression</replac
5252
[ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ] [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ] ]
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[ LATERAL ] ( <replaceable class="parameter">select</replaceable> ) [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ]
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<replaceable class="parameter">with_query_name</replaceable> [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ] ]
55-
[ LATERAL ] <replaceable class="parameter">function_name</replaceable> ( [ <replaceable class="parameter">argument</replaceable> [, ...] ] ) [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] | <replaceable class="parameter">column_definition</replaceable> [, ...] ) ]
55+
[ LATERAL ] <replaceable class="parameter">function_name</replaceable> ( [ <replaceable class="parameter">argument</replaceable> [, ...] ] ) [ WITH ORDINALITY ] [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ] ]
56+
[ LATERAL ] <replaceable class="parameter">function_name</replaceable> ( [ <replaceable class="parameter">argument</replaceable> [, ...] ] ) [ AS ] <replaceable class="parameter">alias</replaceable> ( <replaceable class="parameter">column_definition</replaceable> [, ...] )
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[ LATERAL ] <replaceable class="parameter">function_name</replaceable> ( [ <replaceable class="parameter">argument</replaceable> [, ...] ] ) AS ( <replaceable class="parameter">column_definition</replaceable> [, ...] )
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<replaceable class="parameter">from_item</replaceable> [ NATURAL ] <replaceable class="parameter">join_type</replaceable> <replaceable class="parameter">from_item</replaceable> [ ON <replaceable class="parameter">join_condition</replaceable> | USING ( <replaceable class="parameter">join_column</replaceable> [, ...] ) ]
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@@ -368,18 +369,40 @@ TABLE [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ]
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clause. (This is especially useful for functions that return
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result sets, but any function can be used.) This acts as
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though its output were created as a temporary table for the
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duration of this single <command>SELECT</command> command. An
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alias can also be used. If an alias is written, a column alias
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list can also be written to provide substitute names for one
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or more attributes of the function's composite return type. If
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the function has been defined as returning the <type>record</>
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data type, then an alias or the key word <literal>AS</> must
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be present, followed by a column definition list in the form
378-
<literal>( <replaceable
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duration of this single <command>SELECT</command> command.
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When the optional <command>WITH ORDINALITY</command> is
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appended to the function call, a new column is appended after
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all the function call's columns with numbering for each row.
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For example:
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<programlisting>
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SELECT * FROM unnest(ARRAY['a','b','c','d','e','f']) WITH ORDINALITY;
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unnest | ordinality
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--------+----------
381+
a | 1
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b | 2
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c | 3
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d | 4
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e | 5
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f | 6
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(6 rows)
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</programlisting>
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An alias can also be used. If an alias is written, a column
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alias list can also be written to provide substitute names for
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one or more attributes of the function's composite return
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type, including the column added by <literal>ORDINALITY</literal>
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if present.
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</para>
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<para>
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If the function has been defined as returning the
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<type>record</> data type, then an alias or the key word
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<literal>AS</> must be present, followed by a column
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definition list in the form <literal>( <replaceable
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class="parameter">column_name</replaceable> <replaceable
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class="parameter">data_type</replaceable> <optional>, ... </>
381-
)</literal>. The column definition list must match the actual
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number and types of columns returned by the function.
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class="parameter">data_type</replaceable> <optional>, ...
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</>)</literal>. The column definition list must match the
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actual number and types of columns returned by the function.
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<literal>ORDINALITY</literal> does not work in this case.
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</para>
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</listitem>
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</varlistentry>

‎src/backend/access/common/tupdesc.c

Lines changed: 34 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -157,6 +157,40 @@ CreateTupleDescCopy(TupleDesc tupdesc)
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return desc;
158158
}
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/*
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* CreateTupleDescCopyExtend
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* This function creates a new TupleDesc by copying from an existing
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* TupleDesc, but adding space for more columns. The new tupdesc is
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* not regarded as the same record type as the old one (and therefore
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* does not inherit its typeid/typmod, which instead are left as an
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* anonymous record type).
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*
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* The additional column slots are not initialized in any way;
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* callers must do their own TupleDescInitEntry on each.
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*
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* !!! Constraints and defaults are not copied !!!
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*/
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TupleDesc
174+
CreateTupleDescCopyExtend(TupleDesc tupdesc, int moreatts)
175+
{
176+
TupleDesc desc;
177+
int i;
178+
int src_natts = tupdesc->natts;
179+
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Assert(moreatts >= 0);
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desc = CreateTemplateTupleDesc(src_natts + moreatts, tupdesc->tdhasoid);
183+
184+
for (i = 0; i < src_natts; i++)
185+
{
186+
memcpy(desc->attrs[i], tupdesc->attrs[i], ATTRIBUTE_FIXED_PART_SIZE);
187+
desc->attrs[i]->attnotnull = false;
188+
desc->attrs[i]->atthasdef = false;
189+
}
190+
191+
return desc;
192+
}
193+
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/*
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* CreateTupleDescCopyConstr
162196
* This function creates a new TupleDesc by copying from an existing

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