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1 | | -<!-- $PostgreSQL: pgsql/doc/src/sgml/array.sgml,v 1.42 2004/12/23 05:37:39 tgl Exp $ --> |
| 1 | +<!-- $PostgreSQL: pgsql/doc/src/sgml/array.sgml,v 1.43 2005/02/06 20:59:30 tgl Exp $ --> |
2 | 2 |
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3 | 3 | <sect1 id="arrays"> |
4 | 4 | <title>Arrays</title> |
@@ -149,7 +149,7 @@ INSERT INTO sal_emp |
149 | 149 | A limitation of the present array implementation is that individual |
150 | 150 | elements of an array cannot be SQL null values. The entire array |
151 | 151 | can be set to null, but you can't have an array with some elements |
152 | | - null and some not. |
| 152 | + null and some not. (This is likely to change in the future.) |
153 | 153 | </para> |
154 | 154 |
|
155 | 155 | <para> |
@@ -261,6 +261,18 @@ SELECT schedule[1:2][2] FROM sal_emp WHERE name = 'Bill'; |
261 | 261 | </programlisting> |
262 | 262 | </para> |
263 | 263 |
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| 264 | + <para> |
| 265 | + Fetching from outside the current bounds of an array yields a |
| 266 | + SQL null value, not an error. For example, if <literal>schedule</> |
| 267 | + currently has the dimensions <literal>[1:3][1:2]</> then referencing |
| 268 | + <literal>schedule[3][3]</> yields NULL. Similarly, an array reference |
| 269 | + with the wrong number of subscripts yields a null rather than an error. |
| 270 | + Fetching an array slice that |
| 271 | + is completely outside the current bounds likewise yields a null array; |
| 272 | + but if the requested slice partially overlaps the array bounds, then it |
| 273 | + is silently reduced to just the overlapping region. |
| 274 | + </para> |
| 275 | + |
264 | 276 | <para> |
265 | 277 | The current dimensions of any array value can be retrieved with the |
266 | 278 | <function>array_dims</function> function: |
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