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Prepare for 6.4.1.
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Bruce Momjian
63
doc/FAQ
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doc/FAQ
@ -1,7 +1,7 @@
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Frequently Asked Questions (FAQ) for PostgreSQL
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Last updated: Sat Oct 24 00:12:23 EDT 1998
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Last updated: Sat Dec 12 22:56:56 EST 1998
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Current maintainer: Bruce Momjian (maillist@candle.pha.pa.us)
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@ -68,8 +68,7 @@
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cursors?
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3.5) What is an R-tree index and what is it used for?
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3.6) What is the maximum size for a tuple?
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3.7) I defined indices but my queries don't seem to make use of them.
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Why?
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3.7) My queries are slow or don't make use of the indexes. Why?
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3.8) How do I do regular expression searches? case-insensitive regexp
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searching?
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3.9) I experienced a server crash during a vacuum. How do I remove the
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@ -275,7 +274,7 @@ Section 1: General Questions
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pg_upgrade utility. Those upgrading from earlier releases require a
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dump and restore.
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Those ugrading from versions earlier than 1.09 must upgrade to 1.09
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Those upgrading from versions earlier than 1.09 must upgrade to 1.09
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first without a dump/reload, then dump the data from 1.09, and then
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load it into 6.4.
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@ -306,14 +305,14 @@ Section 1: General Questions
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PHP is great for simple stuff, but for more complex stuff, some still
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use the perl interface and CGI.pm.
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An WWW gatway based on WDB using perl can be downloaded from
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An WWW gateway based on WDB using perl can be downloaded from
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http://www.eol.ists.ca/~dunlop/wdb-p95
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1.13) Does PostgreSQL have a graphical user interface? A report generator? A
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embedded query language interface?
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We have a nice graphical user interface called pgaccess, which is
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shipped as part of the distribtion. Pgaccess also has a report
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shipped as part of the distribution. Pgaccess also has a report
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generator.
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The web page is http://www.flex.ro/pgaccess We also include ecpg,
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@ -433,7 +432,7 @@ Section 2: Installation Questions
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You can also use the postgres -S option to increase the maximum amount
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of memory used by each backend process for temporary sorts. Each
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buffer is 1K and the defualt is 512 buffers.
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buffer is 1K and the default is 512 buffers.
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You can also use the cluster command to group data in base tables to
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match an index. See the cluster(l) manual page for more details.
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@ -471,7 +470,7 @@ Section 2: Installation Questions
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operating system can attach to a running backend directly to diagnose
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problems.
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The postgres program has a -s, -A, -t options that can be very usefull
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The postgres program has a -s, -A, -t options that can be very useful
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for debugging and performance measurements.
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You can also compile with profiling to see what functions are taking
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@ -483,7 +482,7 @@ Section 2: Installation Questions
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Edit include/storage/sinvaladt.h, and change the value of
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MaxBackendId. In the future, we plan to make this a configurable
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prameter.
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parameter.
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2.14) What non-unix ports are available?
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@ -492,12 +491,16 @@ Section 2: Installation Questions
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the client is running on MS Windows, and communicates via TCP/IP to a
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server running on one of our supported Unix platforms.
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A file win32.mak is included in the distributiion for making a Win32
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A file win32.mak is included in the distribution for making a Win32
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libpq library and psql.
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Someone is attempting to port our PostgreSQL database server to
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Windows NT using the Cygnus Unix/NT porting library. He has gotten it
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compiled, but initdb is currently failing.
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The database server is now working on Windows NT using the Cygnus
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Unix/NT porting library. The only feature missing is dynamic loading
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of user-defined functions/types. See
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http://www.askesis.nl/AskesisPostgresIndex.html for more information.
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There is another port using U/Win at
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http://surya.wipro.com/uwin/ported.html.
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_________________________________________________________________
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Section 3: PostgreSQL Features
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@ -569,22 +572,28 @@ Section 3: PostgreSQL Features
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Tuples do not cross 8k boundaries so a 5k tuple will require 8k of
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storage.
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3.7) I defined indices but my queries don't seem to make use of them. Why?
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3.7) My queries are slow or don't make use of the indexes. Why?
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PostgreSQL does not automatically maintain statistics. One has to make
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an explicit vacuum call to update the statistics. After statistics are
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updated, the optimizer knows how many rows in the table, and can
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better decide if it should use indices. Note that the optimizer does
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not use indices in cases when the table is small because a sequentail
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scan would be faster. For column-specific optimization statistics, use
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vacuum analyze.
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not use indices in cases when the table is small because a sequential
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scan would be faster.
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For column-specific optimization statistics, use vacuum analyze.
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Vacuum analyze is important for complex multi-join queries, so the
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optimizer can estimate the number of rows returned from each table,
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and choose the proper join order. The backend does not keep track of
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column statistics on its own, and vacuum analyze must be run to
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collect them periodically.
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Indexes are not used for order by operations.
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When using wildcard operators like LIKE or ~, indices can only be used
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if the beginning of the search is anchored to the start of the string.
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So, to use indices, LIKE searches can should not begin with %, and
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~(regular expression searches) should start with ^.
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When using wild-card operators like LIKE or ~, indices can only be
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used if the beginning of the search is anchored to the start of the
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string. So, to use indices, LIKE searches can should not begin with %,
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and ~(regular expression searches) should start with ^.
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3.8) How do I do regular expression searches? case-insensitive regexp
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searching?
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@ -681,9 +690,9 @@ BYTEA bytea variable-length array of bytes
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CREATE TABLE new_table (mycol int);
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INSERT INTO new_table SELECT oid, mycol FROM old_table;
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Tids are used to indentify specific physical rows with block and
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offset values. Tids change after rows are modified or reloaded. They
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are used by index entries to point to physical rows.
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Tids are used to identify specific physical rows with block and offset
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values. Tids change after rows are modified or reloaded. They are used
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by index entries to point to physical rows.
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3.18) What is the meaning of some of the terms used in PostgreSQL?
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@ -794,10 +803,8 @@ Section 4: Extending PostgreSQL
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4.2) I get messages of the type NOTICE:PortalHeapMemoryFree: 0x402251d0 not
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in alloc set!
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You are pfree'ing something that was not palloc'ed. When writing
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user-defined functions, do not include the file "libpq-fe.h". Doing so
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will cause your palloc to be a malloc instead of a free. Then, when
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the backend pfrees the storage, you get the notice message.
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You are pfree'ing something that was not palloc'ed. Beware of mixing
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malloc/free and palloc/pfree.
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4.3) I've written some nifty new types and functions for PostgreSQL.
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