<div dir="ltr">Hi,<div><br></div><div>AFAIU, the restriction on partitioned tables is even bigger. From PG doc (<a href="http://www.postgresql.org/docs/current/interactive/ddl-partitioning.html#DDL-PARTITIONING-CONSTRAINT-EXCLUSION">http://www.postgresql.org/docs/current/interactive/ddl-partitioning.html#DDL-PARTITIONING-CONSTRAINT-EXCLUSION</a>) :</div><div><br></div><div>"<span style="color:rgb(0,0,0);font-family:verdana,sans-serif;font-size:12.16px;line-height:1.5em">The following caveats apply to constraint exclusion:</span></div><ul style="font-size:12.16px;line-height:1.5em;margin-top:0.2em;margin-bottom:0.1em;color:rgb(0,0,0);font-family:verdana,sans-serif"><li style="font-size:1em;line-height:1.5em;margin-top:0.2em;margin-bottom:0.1em"><p style="font-size:1em;line-height:1.5em;margin:0.2em 0em 1.2em">Constraint exclusion only works when the query's <tt class="" style="font-size:1.3em">WHERE</tt> clause contains constants (or externally supplied parameters). For example, a comparison against a non-immutable function such as<code class="" style="font-size:1.3em">CURRENT_TIMESTAMP</code> cannot be optimized, since the planner cannot know which partition the function value might fall into at run time.</p></li></ul><div>"</div><div>Using a subquery to provide values won't trigger the constraint exclusion.<br></div><div>One solution could be an anonymous block or a function to explicitly write query with constant values got from a previous query.</div><div><br></div><div>Rubio, take also care that a lot of partitioned tables is not recommended by Pg doc:</div><div>"<span style="color:rgb(0,0,0);font-family:verdana,sans-serif;font-size:12.16px;line-height:18.24px">All constraints on all partitions of the master table are examined during constraint exclusion, so large numbers of partitions are likely to increase query planning time considerably. Partitioning using these techniques will work well with up to perhaps a hundred partitions; don't try to use many thousands of partitions.</span>"</div><div><br></div><div>I would go for a smaller set of bigger tables (10's millions rows or so).</div><div><br></div><div>Nicolas </div></div><div class="gmail_extra"><br><div class="gmail_quote">On 2 November 2015 at 18:28, Bborie Park <span dir="ltr"><<a href="mailto:dustymugs@gmail.com" target="_blank">dustymugs@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">That check constraint is not going to help you as it is too complicated for the partitioning task. I don't believe the partitioning constraint can be functional but needs to be simpler and built upon a basic data type...<div><br></div><div>Something like...</div><div><br></div><font face="monospace, monospace">CREATE TABLE max_extent AS (<br> id integer PRIMARY KEY,<br> geom geometry(POLYGON)<br>);</font><div><br></div><div>And then the parent/partition tables had a reference to pc_extent...</div><div><br></div><font face="monospace, monospace"><span class="">CREATE TABLE ahn3_pointcloud.ahn3_all<br>(<br> id integer NOT NULL,<br></span> pa pcpatch(7),</font><div><font face="monospace, monospace"> max_extent_id integer<br>);</font></div><div><br></div><div>Then your queries become...</div><div><br></div><div><font face="monospace, monospace">WITH max_extents AS (</font></div><font face="monospace, monospace">SELECT</font><div><font face="monospace, monospace"> id<br></font><div><font face="monospace, monospace">FROM max_extent<br>WHERE PC_Intersects(geom, ST_MakeEnvelope(120740,486076,121074,486292, 28992))</font></div><div><font face="monospace, monospace">)</font></div><div><font face="monospace, monospace">SELECT<br>*</font></div><div><font face="monospace, monospace">FROM ahn3_all</font></div><div><font face="monospace, monospace">JOIN max_extents</font></div><div><font face="monospace, monospace"> ON ahn3_all.max_extent_id = <a href="http://max_extents.id" target="_blank">max_extents.id</a></font></div><div><span style="font-family:monospace,monospace"><br></span></div><div><div>-bborie</div></div></div><div class="gmail_extra"><br><div class="gmail_quote"><div><div class="h5">On Mon, Nov 2, 2015 at 8:45 AM, Rubio Vaughan <span dir="ltr"><<a href="mailto:rubio.vaughan@geodan.nl" target="_blank">rubio.vaughan@geodan.nl</a>></span> wrote:<br></div></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><div><div class="h5">
<div bgcolor="#FFFFFF" text="#000000">
Dear all,<br>
<br>
We are trying to load a large LIDAR pointcloud dataset into multiple
tables in PostGIS, using the point cloud extension. Eventually the
whole data set will consist of 1400+ tables, containing about 1
million records each. Using a union view on all these tables would
result in terrible performance, which is why we are trying to
optimize query performance using partitioned tables. According to
the documentation, the use of partitioned tables with CHECK
constraints should cause the query planner to only scan those tables
for which the CHECK constraint matches. Excerpt from the
documentation:<br>
--------------------------------------------------------------------------------<br>
<b>18.7.4. Other Planner Options</b><br>
<tt style="font-size:1.3em;color:rgb(0,0,0);font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:left;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255)">constraint_exclusion</tt><span style="color:rgb(0,0,0);font-family:verdana,sans-serif;font-size:12.16px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:left;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;float:none;display:inline!important;background-color:rgb(255,255,255)"><span> </span>(</span><tt style="font-size:1.3em;color:rgb(0,0,0);font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:left;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255)">enum</tt><span style="color:rgb(0,0,0);font-family:verdana,sans-serif;font-size:12.16px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:left;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;float:none;display:inline!important;background-color:rgb(255,255,255)">):
Controls the query planner's use of table constraints to optimize
queries. The allowed values of constraint_exclusion are on
(examine constraints for all tables), off (never examine
constraints), and partition (examine constraints only for
inheritance child tables and UNION ALL subqueries). partition is
the default setting. It is often used with inheritance and
partitioned tables to improve performance. When this parameter
allows it for a particular table, the planner compares query
conditions with the table's CHECK constraints, and omits scanning
tables for which the conditions contradict the constraints.</span><br>
--------------------------------------------------------------------------------<br>
<br>
However, as you can see from the example query below, the indexes
for all child tables are still scanned. I would expect the query
planner to only scan table c_25gn1, which contains the queried
region. Does anyone here have experience with partitioned tables? I
would be delighted to get some pointers for figuring out this
problem.<br>
<br>
Thanks in advance for any help!<br>
<br>
Best regards,<br>
Rubio Vaughan<br>
<br>
<b>General info:</b><b><br>
</b><tt>-------------------</tt><tt><tt>----------</tt></tt><tt><tt><tt>----------</tt></tt></tt><tt><tt><tt><tt>----------</tt></tt></tt></tt><tt><tt><tt><tt><tt>----------</tt></tt></tt></tt></tt><tt><tt><tt><tt><tt><tt>----------</tt></tt></tt></tt></tt></tt><tt><tt><tt><tt><tt><tt><tt>----------</tt></tt></tt></tt></tt></tt>-</tt><tt></tt><tt><br>
SELECT postgis_full_version();<br>
"POSTGIS="2.2.0 r14208" GEOS="3.5.0-CAPI-1.9.0 r4084"
SFCGAL="1.2.0" PROJ="Rel. 4.8.0, 6 March 2012" GDAL="GDAL 2.0.1,
released 2015/09/15" LIBXML="2.9.1" LIBJSON="0.11.99" TOPOLOGY
(topology procs from "2.1.4 r12966" need upgrade) RASTER"<br>
<br>
SHOW "constraint_exclusion";<br>
"partition"<br>
</tt><tt>-------------------</tt><tt><tt>----------</tt></tt><tt><tt><tt>----------</tt></tt></tt><tt><tt><tt><tt>----------</tt></tt></tt></tt><tt><tt><tt><tt><tt>----------</tt></tt></tt></tt></tt><tt><tt><tt><tt><tt><tt>----------</tt></tt></tt></tt></tt></tt><tt><tt><tt><tt><tt><tt><tt>----------</tt></tt></tt></tt></tt></tt>-</tt><tt><br>
</tt><br>
<b>The parent table:</b><br>
<tt><tt>-------------------</tt><tt><tt>----------</tt></tt><tt><tt><tt>----------</tt></tt></tt><tt><tt><tt><tt>----------</tt></tt></tt></tt><tt><tt><tt><tt><tt>----------</tt></tt></tt></tt></tt><tt><tt><tt><tt><tt><tt>----------</tt></tt></tt></tt></tt></tt><tt><tt><tt><tt><tt><tt><tt>----------</tt></tt></tt></tt></tt></tt>-</tt><tt><br>
</tt>CREATE TABLE ahn3_pointcloud.ahn3_all<br>
(<br>
</tt><tt><tt> </tt>id integer NOT NULL,<br>
</tt><tt><tt> </tt>pa pcpatch(7)<br>
)<br>
</tt><tt>-------------------</tt><tt><tt>----------</tt></tt><tt><tt><tt>----------</tt></tt></tt><tt><tt><tt><tt>----------</tt></tt></tt></tt><tt><tt><tt><tt><tt>----------</tt></tt></tt></tt></tt><tt><tt><tt><tt><tt><tt>----------</tt></tt></tt></tt></tt></tt><tt><tt><tt><tt><tt><tt><tt>----------</tt></tt></tt></tt></tt></tt>-</tt><tt><br>
</tt><br>
<b>One of the child tables:</b><br>
<tt><tt>-------------------</tt><tt><tt>----------</tt></tt><tt><tt><tt>----------</tt></tt></tt><tt><tt><tt><tt>----------</tt></tt></tt></tt><tt><tt><tt><tt><tt>----------</tt></tt></tt></tt></tt><tt><tt><tt><tt><tt><tt>----------</tt></tt></tt></tt></tt></tt><tt><tt><tt><tt><tt><tt><tt>----------</tt></tt></tt></tt></tt></tt>-</tt><tt><br>
</tt>CREATE TABLE ahn3_pointcloud.c_25dn2<br>
(<br>
id serial NOT NULL,<br>
pa pcpatch(7),<br>
CONSTRAINT c_25dn2_pkey PRIMARY KEY (id),<br>
CONSTRAINT check_extent CHECK (pc_intersects(pa,
st_geomfromtext('POLYGON((115000 487500,120000 487500,120000
481250,115000 481250,115000 487500))'::text, 28992)))<br>
)<br>
INHERITS (ahn3_pointcloud.ahn3_all)<br>
</tt><tt>-------------------</tt><tt><tt>----------</tt></tt><tt><tt><tt>----------</tt></tt></tt><tt><tt><tt><tt>----------</tt></tt></tt></tt><tt><tt><tt><tt><tt>----------</tt></tt></tt></tt></tt><tt><tt><tt><tt><tt><tt>----------</tt></tt></tt></tt></tt></tt><tt><tt><tt><tt><tt><tt><tt>----------</tt></tt></tt></tt></tt></tt>-</tt><tt><br>
</tt><br>
<b>Example query:</b><br>
<tt><tt>-------------------</tt><tt><tt>----------</tt></tt><tt><tt><tt>----------</tt></tt></tt><tt><tt><tt><tt>----------</tt></tt></tt></tt><tt><tt><tt><tt><tt>----------</tt></tt></tt></tt></tt><tt><tt><tt><tt><tt><tt>----------</tt></tt></tt></tt></tt></tt><tt><tt><tt><tt><tt><tt><tt>----------</tt></tt></tt></tt></tt></tt>-</tt><tt><br>
</tt>EXPLAIN SELECT COUNT(pa) FROM ahn3_pointcloud.ahn3_all <br>
WHERE PC_Intersects(pa,
ST_MakeEnvelope(120740,486076,121074,486292, 28992))<br>
<br>
"Aggregate (cost=301989.36..301989.37 rows=1 width=32)"<br>
" -> Append (cost=0.00..301248.82 rows=296216 width=32)"<br>
" -> Seq Scan on ahn3_all (cost=0.00..0.00 rows=1
width=32)"<br>
" Filter:
(('010300002040710000010000000500000000000000407AFD4000000000<snip><br>
" -> Bitmap Heap Scan on c_25gn1
(cost=6064.85..59546.09 rows=58574 width=32)"<br>
" Recheck Cond:
('010300002040710000010000000500000000000000407AFD40000<snip><br>
" Filter:
_st_intersects('010300002040710000010000000500000000000000407<snip><br>
" -> Bitmap Index Scan on c_25gn1_idx
(cost=0.00..6050.20 rows=175722 width=0)"<br>
" Index Cond:
('010300002040710000010000000500000000000000407AFD4<snip><br>
" -> Bitmap Heap Scan on c_30fz1
(cost=7990.39..77907.99 rows=76576 width=32)"<br>
" Recheck Cond:
('010300002040710000010000000500000000000000407AFD40000<snip><br>
" Filter:
_st_intersects('010300002040710000010000000500000000000000407<snip><br>
" -> Bitmap Index Scan on c_30fz1_idx
(cost=0.00..7971.24 rows=229727 width=0)"<br>
" Index Cond:
('010300002040710000010000000500000000000000407AFD4<snip><br>
" -> Bitmap Heap Scan on c_30fz2
(cost=7393.57..71499.52 rows=70210 width=32)"<br>
" Recheck Cond:
('010300002040710000010000000500000000000000407AFD40000<snip><br>
" Filter:
_st_intersects('010300002040710000010000000500000000000000407<snip><br>
" -> Bitmap Index Scan on c_30fz2_idx
(cost=0.00..7376.02 rows=210631 width=0)"<br>
" Index Cond:
('010300002040710000010000000500000000000000407AFD4<snip><br>
" -> Bitmap Heap Scan on c_25ez1
(cost=2624.69..26079.63 rows=25688 width=32)"<br>
" Recheck Cond:
('010300002040710000010000000500000000000000407AFD40000<snip><br>
" Filter:
_st_intersects('010300002040710000010000000500000000000000407<snip><br>
" -> Bitmap Index Scan on c_25ez1_idx
(cost=0.00..2618.27 rows=77064 width=0)"<br>
" Index Cond:
('010300002040710000010000000500000000000000407AFD4<snip><br>
" -> Bitmap Heap Scan on c_25dn2
(cost=6714.83..66215.58 rows=65167 width=32)"<br>
" Recheck Cond:
('010300002040710000010000000500000000000000407AFD40000<snip><br>
" Filter:
_st_intersects('010300002040710000010000000500000000000000407<snip><br>
" -> Bitmap Index Scan on c_25dn2_idx
(cost=0.00..6698.54 rows=195500 width=0)"<br>
" Index Cond:
('010300002040710000010000000500000000000000407AFD4<snip><br>
</tt><tt>-------------------</tt><tt><tt>----------</tt></tt><tt><tt><tt>----------</tt></tt></tt><tt><tt><tt><tt>----------</tt></tt></tt></tt><tt><tt><tt><tt><tt>----------</tt></tt></tt></tt></tt><tt><tt><tt><tt><tt><tt>----------</tt></tt></tt></tt></tt></tt><tt><tt><tt><tt><tt><tt><tt>----------</tt></tt></tt></tt></tt></tt>-</tt><tt><br>
</tt><br>
<br>
<br>
</div>
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