Update documentation

knizhnik · knizhnik · commit 35fa7a4e4257 · 2017-02-16T19:58:26.000+03:00
diff --git a/tpch.sql b/tpch.sql
@@ -149,7 +149,7 @@ where filter(betwixt(l_shipdate, '1996-01-01', '1997-01-01')
 select
     sum(l_extendedprice*l_discount) as revenue
 from
-    lineitem_projection
+    vops_lineitem_projection
 where
     l_shipdate between '1996-01-01'::date and '1997-01-01'::date
     and l_discount between 0.08 and 0.1
diff --git a/vops.html b/vops.html
@@ -566,7 +566,12 @@ <h2><a name="transform">Standard SQL query transformation</a></h2>
 generate dummy tile with all components equal to the specified constant and perform 
 (<i>vector</i> <b>OP</b> <i>vector</i>) operation instead of more efficient (<i>vector</i> <b>OP</b> <i>scalar</i>).
 </p>
-
+<p>
+There is one pitfall with post parse analyze hook: it is initialized in the extension <code>_PG_init</code> function.
+But if extension was not registered in <code>shared_preload_libraries</code> list, then it will be loaded on demand when any function of this extension is requested.
+Unfortunately it happens <b>after</b> parse analyze is done. So first time you execute VOPS query, it will not be transformed. You can get wrong result in this case.
+Either take it in account, either add <code>vops</code> to <code>shared_preload_libraries</code> configuration string.
+</p>
 
 <h2><a name="example">Example</a></h2>
 
