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Add string_to_table() function.

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This splits a string at occurrences of a delimiter.  It is exactly like
string_to_array() except for producing a set of values instead of an
array of values.  Thus, the relationship of these two functions is
the same as between regexp_split_to_table() and regexp_split_to_array().

Although the same results could be had from unnest(string_to_array()),
this is somewhat faster than that, and anyway it seems reasonable to
have it for symmetry with the regexp functions.

Pavel Stehule, reviewed by Peter Smith

Discussion: https://postgr.es/m/CAFj8pRD8HOpjq2TqeTBhSo_QkzjLOhXzGCpKJ4nCs7Y9SQkuPw@mail.gmail.com
This commit is contained in:
Tom Lane
2020-09-02 18:23:56 -04:00
parent fd5e3b2914
commit 66f1630680
6 changed files with 354 additions and 93 deletions
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90
doc/src/sgml/func.sgml
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@@ -3220,7 +3220,7 @@ repeat('Pg', 4) <returnvalue>PgPgPgPg</returnvalue>
</para>
<para>
Splits <parameter>string</parameter> using a POSIX regular
expression as the delimiter; see
expression as the delimiter, producing an array of results; see
<xref linkend="functions-posix-regexp"/>.
</para>
<para>
@@ -3239,7 +3239,7 @@ repeat('Pg', 4) <returnvalue>PgPgPgPg</returnvalue>
</para>
<para>
Splits <parameter>string</parameter> using a POSIX regular
expression as the delimiter; see
expression as the delimiter, producing a set of results; see
<xref linkend="functions-posix-regexp"/>.
</para>
<para>
@@ -3460,6 +3460,65 @@ repeat('Pg', 4) <returnvalue>PgPgPgPg</returnvalue>
</para></entry>
</row>
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
<primary>string_to_array</primary>
</indexterm>
<function>string_to_array</function> ( <parameter>string</parameter> <type>text</type>, <parameter>delimiter</parameter> <type>text</type> <optional>, <parameter>null_string</parameter> <type>text</type> </optional> )
<returnvalue>text[]</returnvalue>
</para>
<para>
Splits the <parameter>string</parameter> at occurrences
of <parameter>delimiter</parameter> and forms the resulting fields
into a <type>text</type> array.
If <parameter>delimiter</parameter> is <literal>NULL</literal>,
each character in the <parameter>string</parameter> will become a
separate element in the array.
If <parameter>delimiter</parameter> is an empty string, then
the <parameter>string</parameter> is treated as a single field.
If <parameter>null_string</parameter> is supplied and is
not <literal>NULL</literal>, fields matching that string are
replaced by <literal>NULL</literal>.
</para>
<para>
<literal>string_to_array('xx~~yy~~zz', '~~', 'yy')</literal>
<returnvalue>{xx,NULL,zz}</returnvalue>
</para></entry>
</row>
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
<primary>string_to_table</primary>
</indexterm>
<function>string_to_table</function> ( <parameter>string</parameter> <type>text</type>, <parameter>delimiter</parameter> <type>text</type> <optional>, <parameter>null_string</parameter> <type>text</type> </optional> )
<returnvalue>setof text</returnvalue>
</para>
<para>
Splits the <parameter>string</parameter> at occurrences
of <parameter>delimiter</parameter> and returns the resulting fields
as a set of <type>text</type> rows.
If <parameter>delimiter</parameter> is <literal>NULL</literal>,
each character in the <parameter>string</parameter> will become a
separate row of the result.
If <parameter>delimiter</parameter> is an empty string, then
the <parameter>string</parameter> is treated as a single field.
If <parameter>null_string</parameter> is supplied and is
not <literal>NULL</literal>, fields matching that string are
replaced by <literal>NULL</literal>.
</para>
<para>
<literal>string_to_table('xx~^~yy~^~zz', '~^~', 'yy')</literal>
<returnvalue></returnvalue>
<programlisting>
xx
NULL
zz
</programlisting>
</para></entry>
</row>
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
@@ -17819,33 +17878,6 @@ SELECT NULLIF(value, '(none)') ...
</para></entry>
</row>
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
<primary>string_to_array</primary>
</indexterm>
<function>string_to_array</function> ( <parameter>string</parameter> <type>text</type>, <parameter>delimiter</parameter> <type>text</type> <optional>, <parameter>null_string</parameter> <type>text</type> </optional> )
<returnvalue>text[]</returnvalue>
</para>
<para>
Splits the <parameter>string</parameter> at occurrences
of <parameter>delimiter</parameter> and forms the remaining data
into a <type>text</type> array.
If <parameter>delimiter</parameter> is <literal>NULL</literal>,
each character in the <parameter>string</parameter> will become a
separate element in the array.
If <parameter>delimiter</parameter> is an empty string, then
the <parameter>string</parameter> is treated as a single field.
If <parameter>null_string</parameter> is supplied and is
not <literal>NULL</literal>, fields matching that string are converted
to <literal>NULL</literal> entries.
</para>
<para>
<literal>string_to_array('xx~~yy~~zz', '~~', 'yy')</literal>
<returnvalue>{xx,NULL,zz}</returnvalue>
</para></entry>
</row>
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>