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Update FAQ.
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doc/FAQ
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doc/FAQ
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@ -83,12 +83,14 @@
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other users?
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4.17) What is an OID? What is a TID?
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4.18) What is the meaning of some of the terms used in PostgreSQL?
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4.19) How do I tell what PostgreSQL version I am running?
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4.20) My large-object operations get invalid large obj descriptor.
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4.19) Why do I get the error "ERROR: Memory exhausted in
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AllocSetAlloc()?"
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4.20) How do I tell what PostgreSQL version I am running?
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4.21) My large-object operations get invalid large obj descriptor.
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Why?
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4.21) How do I create a column that will default to the current time?
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4.22) Why are my subqueries using IN so slow?
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4.23) How do I perform an outer join?
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4.22) How do I create a column that will default to the current time?
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4.23) Why are my subqueries using IN so slow?
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4.24) How do I perform an outer join?
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Extending PostgreSQL
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@ -97,7 +99,7 @@
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5.2) How can I contribute some nifty new types and functions to
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PostgreSQL?
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5.3) How do I write a C function to return a tuple?
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5.4) I have changed a source file. Why does the recompile not see the
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5.3) I have changed a source file. Why does the recompile not see the
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change?
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_________________________________________________________________
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@ -883,11 +885,26 @@ BYTEA bytea variable-length byte array (null-safe)
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A list of general database terms can be found at:
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http://www.comptechnews.com/~reaster/dbdesign.html
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4.19) How do I tell what PostgreSQL version I am running?
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4.19) Why do I get the error "ERROR: Memory exhausted in AllocSetAlloc()?"
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It is possible you have run out of virtual memory on your system, or
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your kernel has a low limit for certain resources. Try this before
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starting the postmaster:
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ulimit -d 262144
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limit datasize 256m
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Depending on your shell, only one of these may succeed, but it will
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set your process data segment limit much higher and perhaps allow the
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query to complete. This command applies to the current process, and
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all subprocesses created after the command is run. If you are having a
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problem with the SQL client because the backend is returning too much
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data, try it before starting the client.
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4.20) How do I tell what PostgreSQL version I am running?
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From psql, type select version();
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4.20) My large-object operations get invalid large obj descriptor. Why?
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4.21) My large-object operations get invalid large obj descriptor. Why?
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You need to put BEGIN WORK and COMMIT around any use of a large object
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handle, that is, surrounding lo_open ... lo_close.
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@ -901,12 +918,12 @@ BYTEA bytea variable-length byte array (null-safe)
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If you are using a client interface like ODBC you may need to set
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auto-commit off.
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4.21) How do I create a column that will default to the current time?
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4.22) How do I create a column that will default to the current time?
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Use now():
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CREATE TABLE test (x int, modtime timestamp DEFAULT now() );
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4.22) Why are my subqueries using IN so slow?
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4.23) Why are my subqueries using IN so slow?
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Currently, we join subqueries to outer queries by sequentially
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scanning the result of the subquery for each row of the outer query. A
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@ -922,7 +939,7 @@ SELECT *
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We hope to fix this limitation in a future release.
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4.23) How do I perform an outer join?
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4.24) How do I perform an outer join?
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PostgreSQL 7.1 and later supports outer joins using the SQL standard
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syntax. Here are two examples:
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@ -127,15 +127,17 @@
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<SMALL>TID</SMALL>?<BR>
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<A href="#4.18">4.18</A>) What is the meaning of some of the terms
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used in PostgreSQL?<BR>
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<A href="#4.19">4.19</A>) How do I tell what PostgreSQL version I
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<A href="#4.19">4.19</A>) Why do I get the error <I>"ERROR:
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Memory exhausted in AllocSetAlloc()?"</I><BR>
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<A href="#4.20">4.20</A>) How do I tell what PostgreSQL version I
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am running? <BR>
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<A href="#4.20">4.20</A>) My large-object operations get
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<A href="#4.21">4.21</A>) My large-object operations get
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<I>invalid large obj descriptor.</I> Why?<BR>
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<A href="#4.21">4.21</A>) How do I create a column that will
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<A href="#4.22">4.22</A>) How do I create a column that will
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default to the current time?<BR>
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<A href="#4.22">4.22</A>) Why are my subqueries using
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<A href="#4.23">4.23</A>) Why are my subqueries using
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<CODE><SMALL>IN</SMALL></CODE> so slow?<BR>
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<A href="#4.23">4.23</A>) How do I perform an outer join?<BR>
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<A href="#4.24">4.24</A>) How do I perform an outer join?<BR>
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<CENTER>
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@ -147,7 +149,7 @@
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and functions to PostgreSQL?<BR>
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<A href="#5.3">5.3</A>) How do I write a C function to return a
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tuple?<BR>
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<A href="#5.4">5.4</A>) I have changed a source file. Why does the
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<A href="#5.4">5.3</A>) I have changed a source file. Why does the
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recompile not see the change?<BR>
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<HR>
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@ -1132,13 +1134,32 @@ BYTEA bytea variable-length byte array (null-safe)
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<P>A list of general database terms can be found at: <A href=
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"http://www.comptechnews.com/~reaster/dbdesign.html">http://www.comptechnews.com/~reaster/dbdesign.html</A></P>
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<H4><A name="4.19">4.19</A>) How do I tell what PostgreSQL version
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<H4><A name="4.19">4.19</A>) Why do I get the error <I>"ERROR:
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Memory exhausted in AllocSetAlloc()?"</I><BR>
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</H4>
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<P>It is possible you have run out of virtual memory on your
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system, or your kernel has a low limit for certain resources. Try
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this before starting the <I>postmaster:</I></P>
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<PRE>
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ulimit -d 262144
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limit datasize 256m
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</PRE>
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Depending on your shell, only one of these may succeed, but it will
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set your process data segment limit much higher and perhaps allow
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the query to complete. This command applies to the current process,
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and all subprocesses created after the command is run. If you are
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having a problem with the <SMALL>SQL</SMALL> client because the
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backend is returning too much data, try it before starting the
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client.
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<H4><A name="4.20">4.20</A>) How do I tell what PostgreSQL version
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I am running?<BR>
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</H4>
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<P>From <I>psql,</I> type <CODE>select version();</CODE></P>
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<H4><A name="4.20">4.20</A>) My large-object operations get
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<H4><A name="4.21">4.21</A>) My large-object operations get
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<I>invalid large obj descriptor.</I> Why?<BR>
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</H4>
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@ -1155,7 +1176,7 @@ BYTEA bytea variable-length byte array (null-safe)
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<P>If you are using a client interface like <SMALL>ODBC</SMALL> you
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may need to set <CODE>auto-commit off.</CODE></P>
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<H4><A name="4.21">4.21</A>) How do I create a column that will
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<H4><A name="4.22">4.22</A>) How do I create a column that will
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default to the current time?<BR>
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</H4>
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@ -1165,7 +1186,7 @@ BYTEA bytea variable-length byte array (null-safe)
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</CODE>
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</PRE>
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<H4><A name="4.22">4.22</A>) Why are my subqueries using
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<H4><A name="4.23">4.23</A>) Why are my subqueries using
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<CODE><SMALL>IN</SMALL></CODE> so slow?<BR>
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</H4>
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@ -1188,7 +1209,7 @@ BYTEA bytea variable-length byte array (null-safe)
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</PRE>
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We hope to fix this limitation in a future release.
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<H4><A name="4.23">4.23</A>) How do I perform an outer join?<BR>
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<H4><A name="4.24">4.24</A>) How do I perform an outer join?<BR>
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</H4>
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<P>PostgreSQL 7.1 and later supports outer joins using the SQL
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