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Add get_bit/set_bit functions for bit strings, paralleling those for bytea,
and implement OVERLAY() for bit strings and bytea. In passing also convert text OVERLAY() to a true built-in, instead of relying on a SQL function. Leonardo F, reviewed by Kevin Grittner
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13 files changed

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‎doc/src/sgml/func.sgml‎

Lines changed: 83 additions & 57 deletions
Original file line numberDiff line numberDiff line change
@@ -1,4 +1,4 @@
1-
<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.497 2010/01/19 05:50:18 tgl Exp $ -->
1+
<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.498 2010/01/25 20:55:32 tgl Exp $ -->
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33
<chapter id="functions">
44
<title>Functions and Operators</title>
@@ -2620,7 +2620,7 @@
26202620
<entry>Return Type</entry>
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<entry>Description</entry>
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<entry>Example</entry>
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<entry>Result</entry>
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<entry>Result</entry>
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</row>
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</thead>
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@@ -2640,32 +2640,6 @@
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<entry><literal>\\Post'gres\000</literal></entry>
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</row>
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2643-
<row>
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<entry><function>get_bit</function>(<parameter>string</parameter>, <parameter>offset</parameter>)</entry>
2645-
<entry><type>int</type></entry>
2646-
<entry>
2647-
Extract bit from string
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<indexterm>
2649-
<primary>get_bit</primary>
2650-
</indexterm>
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</entry>
2652-
<entry><literal>get_bit(E'Th\\000omas'::bytea, 45)</literal></entry>
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<entry><literal>1</literal></entry>
2654-
</row>
2655-
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<row>
2657-
<entry><function>get_byte</function>(<parameter>string</parameter>, <parameter>offset</parameter>)</entry>
2658-
<entry><type>int</type></entry>
2659-
<entry>
2660-
Extract byte from string
2661-
<indexterm>
2662-
<primary>get_byte</primary>
2663-
</indexterm>
2664-
</entry>
2665-
<entry><literal>get_byte(E'Th\\000omas'::bytea, 4)</literal></entry>
2666-
<entry><literal>109</literal></entry>
2667-
</row>
2668-
26692643
<row>
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<entry><literal><function>octet_length</function>(<parameter>string</parameter>)</literal></entry>
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<entry><type>int</type></entry>
@@ -2675,39 +2649,21 @@
26752649
</row>
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<row>
2678-
<entry><literal><function>position</function>(<parameter>substring</parameter> in <parameter>string</parameter>)</literal></entry>
2679-
<entry><type>int</type></entry>
2680-
<entry>Location of specified substring</entry>
2681-
<entry><literal>position(E'\\000om'::bytea in E'Th\\000omas'::bytea)</literal></entry>
2682-
<entry><literal>3</literal></entry>
2683-
</row>
2684-
2685-
<row>
2686-
<entry><function>set_bit</function>(<parameter>string</parameter>,
2687-
<parameter>offset</parameter>, <parameter>newvalue</>)</entry>
2652+
<entry><literal><function>overlay</function>(<parameter>string</parameter> placing <parameter>string</parameter> from <type>int</type> <optional>for <type>int</type></optional>)</literal></entry>
26882653
<entry><type>bytea</type></entry>
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<entry>
2690-
Set bit in string
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<indexterm>
2692-
<primary>set_bit</primary>
2693-
</indexterm>
2655+
Replace substring
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</entry>
2695-
<entry><literal>set_bit(E'Th\\000omas'::bytea, 45, 0)</literal></entry>
2696-
<entry><literal>Th\000omAs</literal></entry>
2657+
<entry><literal>overlay(E'Th\\000omas'::bytea placing E'\\002\\003'::bytea from 2 for 3)</literal></entry>
2658+
<entry><literal>T\\002\\003mas</literal></entry>
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</row>
26982660

26992661
<row>
2700-
<entry><function>set_byte</function>(<parameter>string</parameter>,
2701-
<parameter>offset</parameter>, <parameter>newvalue</>)</entry>
2702-
<entry><type>bytea</type></entry>
2703-
<entry>
2704-
Set byte in string
2705-
<indexterm>
2706-
<primary>set_byte</primary>
2707-
</indexterm>
2708-
</entry>
2709-
<entry><literal>set_byte(E'Th\\000omas'::bytea, 4, 64)</literal></entry>
2710-
<entry><literal>Th\000o@as</literal></entry>
2662+
<entry><literal><function>position</function>(<parameter>substring</parameter> in <parameter>string</parameter>)</literal></entry>
2663+
<entry><type>int</type></entry>
2664+
<entry>Location of specified substring</entry>
2665+
<entry><literal>position(E'\\000om'::bytea in E'Th\\000omas'::bytea)</literal></entry>
2666+
<entry><literal>3</literal></entry>
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</row>
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27132669
<row>
@@ -2784,7 +2740,7 @@
27842740
</entry>
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<entry><type>bytea</type></entry>
27862742
<entry>
2787-
Decode binary string from <parameter>string</parameter> previously
2743+
Decode binary string from <parameter>string</parameter> previously
27882744
encoded with <function>encode</>. Parameter type is same as in <function>encode</>.
27892745
</entry>
27902746
<entry><literal>decode(E'123\\000456', 'escape')</literal></entry>
@@ -2805,6 +2761,36 @@
28052761
<entry><literal>123\000456</literal></entry>
28062762
</row>
28072763

2764+
<row>
2765+
<entry>
2766+
<literal><function>get_bit</function>(<parameter>string</parameter>, <parameter>offset</parameter>)</literal>
2767+
</entry>
2768+
<entry><type>int</type></entry>
2769+
<entry>
2770+
Extract bit from string
2771+
<indexterm>
2772+
<primary>get_bit</primary>
2773+
</indexterm>
2774+
</entry>
2775+
<entry><literal>get_bit(E'Th\\000omas'::bytea, 45)</literal></entry>
2776+
<entry><literal>1</literal></entry>
2777+
</row>
2778+
2779+
<row>
2780+
<entry>
2781+
<literal><function>get_byte</function>(<parameter>string</parameter>, <parameter>offset</parameter>)</literal>
2782+
</entry>
2783+
<entry><type>int</type></entry>
2784+
<entry>
2785+
Extract byte from string
2786+
<indexterm>
2787+
<primary>get_byte</primary>
2788+
</indexterm>
2789+
</entry>
2790+
<entry><literal>get_byte(E'Th\\000omas'::bytea, 4)</literal></entry>
2791+
<entry><literal>109</literal></entry>
2792+
</row>
2793+
28082794
<row>
28092795
<entry><literal><function>length</function>(<parameter>string</parameter>)</literal></entry>
28102796
<entry><type>int</type></entry>
@@ -2834,6 +2820,38 @@
28342820
<entry><literal>md5(E'Th\\000omas'::bytea)</literal></entry>
28352821
<entry><literal>8ab2d3c9689aaf18 b4958c334c82d8b1</literal></entry>
28362822
</row>
2823+
2824+
<row>
2825+
<entry>
2826+
<literal><function>set_bit</function>(<parameter>string</parameter>,
2827+
<parameter>offset</parameter>, <parameter>newvalue</>)</literal>
2828+
</entry>
2829+
<entry><type>bytea</type></entry>
2830+
<entry>
2831+
Set bit in string
2832+
<indexterm>
2833+
<primary>set_bit</primary>
2834+
</indexterm>
2835+
</entry>
2836+
<entry><literal>set_bit(E'Th\\000omas'::bytea, 45, 0)</literal></entry>
2837+
<entry><literal>Th\000omAs</literal></entry>
2838+
</row>
2839+
2840+
<row>
2841+
<entry>
2842+
<literal><function>set_byte</function>(<parameter>string</parameter>,
2843+
<parameter>offset</parameter>, <parameter>newvalue</>)</literal>
2844+
</entry>
2845+
<entry><type>bytea</type></entry>
2846+
<entry>
2847+
Set byte in string
2848+
<indexterm>
2849+
<primary>set_byte</primary>
2850+
</indexterm>
2851+
</entry>
2852+
<entry><literal>set_byte(E'Th\\000omas'::bytea, 4, 64)</literal></entry>
2853+
<entry><literal>Th\000o@as</literal></entry>
2854+
</row>
28372855
</tbody>
28382856
</tgroup>
28392857
</table>
@@ -2934,7 +2952,15 @@
29342952
<literal><function>bit_length</function></literal>,
29352953
<literal><function>octet_length</function></literal>,
29362954
<literal><function>position</function></literal>,
2937-
<literal><function>substring</function></literal>.
2955+
<literal><function>substring</function></literal>,
2956+
<literal><function>overlay</function></literal>.
2957+
</para>
2958+
2959+
<para>
2960+
The following functions work on bit strings as well as binary
2961+
strings:
2962+
<literal><function>get_bit</function></literal>,
2963+
<literal><function>set_bit</function></literal>.
29382964
</para>
29392965

29402966
<para>

‎src/backend/parser/gram.y‎

Lines changed: 4 additions & 3 deletions
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/parser/gram.y,v 2.704 2010/01/22 16:40:18 rhaas Exp $
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* $PostgreSQL: pgsql/src/backend/parser/gram.y,v 2.705 2010/01/25 20:55:32 tgl Exp $
1515
*
1616
* HISTORY
1717
* AUTHOR DATE MAJOR EVENT
@@ -9586,9 +9586,9 @@ func_expr: func_name '(' ')' over_clause
95869586
| OVERLAY '(' overlay_list ')'
95879587
{
95889588
/* overlay(A PLACING B FROM C FOR D) is converted to
9589-
* substring(A, 1, C-1) || B || substring(A, C+1, C+D)
9589+
* overlay(A, B, C, D)
95909590
* overlay(A PLACING B FROM C) is converted to
9591-
* substring(A, 1, C-1) || B || substring(A, C+1, C+char_length(B))
9591+
* overlay(A, B, C)
95929592
*/
95939593
FuncCall *n = makeNode(FuncCall);
95949594
n->funcname = SystemFuncName("overlay");
@@ -10150,6 +10150,7 @@ extract_arg:
1015010150
* SQL99 defines the OVERLAY() function:
1015110151
* o overlay(text placing text from int for int)
1015210152
* o overlay(text placing text from int)
10153+
* and similarly for binary strings
1015310154
*/
1015410155
overlay_list:
1015510156
a_expr overlay_placing substr_from substr_for

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