Last updated: Mon May 30 09:11:03 EDT 2005
+Last updated: Fri Sep 16 14:07:22 EDT 2005
Current maintainer: Bruce Momjian (pgman@candle.pha.pa.us) @@ -26,7 +26,7 @@
PostgreSQL is pronounced Post-Gres-Q-L, also called just - Postgres.
+PostgreSQL is pronounced Post-Gres-Q-L, and is also sometimes + referred to as just Postgres. An audio file is available in + MP3 format for + those would like to hear the pronunciation.
PostgreSQL is an object-relational database system that has the features of traditional commercial database systems with @@ -231,7 +235,7 @@
The latest release of PostgreSQL is version 8.0.2.
+The latest release of PostgreSQL is version 8.0.3.
We plan to have a major release every year, with minor releases every few months.
@@ -613,6 +617,12 @@ table?The maximum table size and maximum number of columns can be quadrupled by increasing the default block size to 32k.
+One limitation is that indexes can not be created on columns + longer than about 2,000 characters. Fortunately, such indexes are + rarely needed. Uniqueness is best guaranteed by a funtion index + of an MD5 hash of the long column, and full text indexing + allows for searching of words within the column.
+
- 32 bytes: each row header (approximate)
+ 28 bytes: each row header (approximate)
24 bytes: one int field and one text field
+ 4 bytes: pointer on page to tuple
----------------------------------------
- 60 bytes per row
+ 56 bytes per row
The data page size in PostgreSQL is 8192 bytes (8 KB), so:
8192 bytes per page
- ------------------- = 136 rows per database page (rounded down)
- 60 bytes per row
+ ------------------- = 146 rows per database page (rounded down)
+ 56 bytes per row
100000 data rows
- -------------------- = 735 database pages (rounded up)
- 128 rows per page
+ -------------------- = 685 database pages (rounded up)
+ 146 rows per page
-735 database pages * 8192 bytes per page = 6,021,120 bytes (6 MB)
+685 database pages * 8192 bytes per page = 5,611,520 bytes (5.6 MB)
Indexes do not require as much overhead, but do contain the data @@ -740,7 +750,12 @@ table?
CREATE INDEX tabindex ON tab (lower(col));
-
+ If the above index is created as UNIQUE, though + the column can store upper and lowercase characters, it can not have + identical values that differ only in case. To force a particular + case to be stored in the column, use a CHECK + constraint or a trigger.
+There are also commercial and hardware-based replication solutions available supporting a variety of replication models.
+ +The most common cause is the use of double-quotes around table or + column names during table creation. When double-quotes are used, + table and column names (called identifiers) are stored case-sensitive, meaning you must use + double-quotes when referencing the names in a query. Some interfaces, + like pgAdmin, automatically double-quote identifiers during table + creation. So, for identifiers to be recognized, you must either: +