Add new FAQ information.

Martijn van Oosterhout

1 files changed, 26 insertions, 1 deletions

diff --git a/doc/FAQ b/doc/FAQ
index d7e2d5ea596..e1c3cf1999a 100644
--- a/doc/FAQ
+++ b/doc/FAQ
@@ -1,7 +1,7 @@
 
                 Frequently Asked Questions (FAQ) for PostgreSQL
                                        
-   Last updated: Fri Jul 29 10:05:09 EDT 2005
+   Last updated: Wed Aug 10 15:29:42 EDT 2005
    
    Current maintainer: Bruce Momjian ([email protected])
    
@@ -79,6 +79,7 @@
    4.19) Why do I get "relation with OID ##### does not exist" errors
    when accessing temporary tables in PL/PgSQL functions?
    4.20) What replication solutions are available?
+   4.21) Why are my table and column names not recognized in my query?
      _________________________________________________________________
    
                              General Questions
@@ -471,6 +472,12 @@
    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 using another column that is an
+   MD5 hash of the long column, and full text indexing allows for
+   searching of words within the column.
+   
   4.5) How much database disk space is required to store data from a typical
   text file?
   
@@ -578,6 +585,11 @@
    expresssion index, it will be used:
     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.
+   
   4.9) In a query, how do I detect if a field is NULL? How can I sort on
   whether a field is NULL or not?
   
@@ -776,3 +788,16 @@
    
    There are also commercial and hardware-based replication solutions
    available supporting a variety of replication models.
+   
+  4.20) Why are my table and column names not recognized in my query?
+  
+   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:
+     * Avoid double-quoting identifiers when creating tables
+     * Use only lowercase characters in identifiers
+     * Double-quote identifiers when referencing them in queries