Re: [GENERAL] Could use some advice on search architecture

[Robin]

On 18/04/2014 21:24, Andy Colson wrote:

On 4/18/2014 8:59 AM, Ron Pasch wrote:

Hello,

I'm contemplating what architecture I should use to make searching as
fast as possible given the information available and the search
requirements. Let me give some background first;

- The database contains products of can potentially have a lot of them
(up to about 3 to 5 million)
- Each product has about 30 different properties defined about them.
Things like what color they are etc. All these properties are enumerated
choices, so for instance for color there is a list of available static
never changing options of which one can be chosen for that product. This
is the same for all those 30 properties. Currently they are stored as
enumerated types (CREATE TYPE propertyvalue AS ENUM ('option1',
'option2', etc..)
- It should be possible to search for products and provide properties
that the product SHOULD have, not must have. For instance, for color,
the search could specify that it should return products that are either
red, blue or green.
- The products that match with the most properties should be in the top
of the search results
- If different products match with the same amount of properties, the
ordering should then be on the product that is most popular. There is
information in the database (and if need be also in the same table)
about how many times a product is sold.
- The results will be paginated per 15 products

The requirement is that these searches should be as fast as possible,
with a maximum of about 200 ms time taken for a search query.

What would be the best approach to this if I were to do this in the
database only? Should/can this be done with postgresql only or should I
look into other types of technology? (Lucene? Sphinx? others?)

Any advice on this would be greatly appreciated.

Thx in advance!

Ron






As we are PG users, on a PG list, we are gonna recommend PG, 
obviously. :-)


Actually though, I recommend PG.


> - The products that match with the most properties should be in the top
> of the search results


That kinda query is going to be really difficult, I think, regardless 
of what you use.  To find that you'll have to measure every product 
(all 5 million) and then sort the results.



> enumerated types (CREATE TYPE propertyvalue AS ENUM ('option1',
> 'option2', etc..)

So, you have something like:

CREATE TYPE colortype AS ENUM ('red', 'green', 'blue');
CREATE TYPE sizetype AS ENUM ('small', 'medium', 'large');

create table product
(
  id serial,
  name text,
  color colortype,
  size  sizetype,
   ...
);


I assume the problem is you don't want to index all 30 properties?  
That makes sense.


> - It should be possible to search for products and provide properties
> that the product SHOULD have, not must have.

I don't understand this.  Say you have a sprocket in red and green.  
Do you want to search for:


select * from product where name = 'sprocket' and (color = 'red' or 
color = 'green')


Or do you want something else?  Does the user say they'd "prefer" 
blue, but will take whatever else you have?


Do you search for some properties exactly and some "preferred"?

Perhaps you could describe a little more how you want to query the 
database?  Or, maybe, what your user's are searching for?


-Andy


Well, given that there are known limited attributes, this is the type of 
application that really really suits a column oriented database, such as 
Sybase IQ (now sold by SAP). Its a neat product that scales. Great 
performance with drag'n'drop analytics.


Unless you can charm IQ out of SAP (it has been known to happen), you 
might have to look at some other techniques


So consider some binary data representation
Red - 1 ( 0001)
Orange - 2 ( 0010)
Yellow - 4 ( 0100)
Green - 8 ( 1000)
Blue - 16 (0001 )
Indigo - 32 (0010 )
Violet - 64 (0100 )

This way, you can encode several colours in 1 value
Red or Green or Indigo = 1 + 8  + 32 = 41 = 0010 1001


Robin


--
Sent via pgsql-general mailing list (pgsql-general@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-general

[GENERAL] Patched odbc_dfw for PG >= 9.2

[Gunnar "Nick" Bluth]

Heillo,

after stumbling across compile errors for odbc_fdw I realised it was 
still on the 9.1. level.


I've patched it, based on the tds_fdw code (so it's still read-only).

It does compile, and I think it is generally sane, however I'm _anything 
but a C hacker_, so whoever feels confident enough please review this, 
or even add the write capability :)


As I've been playing around with tds_fdw before and just wanted to see 
if I can get around my encoding issues with odbc_fdw, I will not be able 
to test it for a few days though.


It is available at
https://github.com/bluthg/odbc_fdw

According notes have been added to the Foreign_data_wrappers WIKI page 
as well (no need for more people to try compiling it ;-).


Cheers,

--
Gunnar "Nick" Bluth
RHCE/SCLA

Mobil   +49 172 8853339
Email: gunnar.bl...@pro-open.de
__
In 1984 mainstream users were choosing VMS over UNIX.  Ten years later
they are choosing Windows over UNIX.  What part of that message aren't you
getting? - Tom Payne



--
Sent via pgsql-general mailing list (pgsql-general@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-general

Re: [GENERAL] Could use some advice on search architecture

[Marc Mamin]

Hi,

Seems that this blog post is worth reading in your case
http://hlinnaka.iki.fi/2014/03/28/gin-as-a-substitute-for-bitmap-indexes/
regards,
Marc Mamin


Von: pgsql-general-ow...@postgresql.org 
[pgsql-general-ow...@postgresql.org]" im Auftrag von "Robin 
[robin...@live.co.uk]
Gesendet: Samstag, 19. April 2014 09:38
An: pgsql-general@postgresql.org
Betreff: Re: [GENERAL] Could use some advice on search architecture

On 18/04/2014 21:24, Andy Colson wrote:
> On 4/18/2014 8:59 AM, Ron Pasch wrote:
>> Hello,
>>
>> I'm contemplating what architecture I should use to make searching as
>> fast as possible given the information available and the search
>> requirements. Let me give some background first;
>>
>> - The database contains products of can potentially have a lot of them
>> (up to about 3 to 5 million)
>> - Each product has about 30 different properties defined about them.
>> Things like what color they are etc. All these properties are enumerated
>> choices, so for instance for color there is a list of available static
>> never changing options of which one can be chosen for that product. This
>> is the same for all those 30 properties. Currently they are stored as
>> enumerated types (CREATE TYPE propertyvalue AS ENUM ('option1',
>> 'option2', etc..)
>> - It should be possible to search for products and provide properties
>> that the product SHOULD have, not must have. For instance, for color,
>> the search could specify that it should return products that are either
>> red, blue or green.
>> - The products that match with the most properties should be in the top
>> of the search results
>> - If different products match with the same amount of properties, the
>> ordering should then be on the product that is most popular. There is
>> information in the database (and if need be also in the same table)
>> about how many times a product is sold.
>> - The results will be paginated per 15 products
>>
>> The requirement is that these searches should be as fast as possible,
>> with a maximum of about 200 ms time taken for a search query.
>>
>> What would be the best approach to this if I were to do this in the
>> database only? Should/can this be done with postgresql only or should I
>> look into other types of technology? (Lucene? Sphinx? others?)
>>
>> Any advice on this would be greatly appreciated.
>>
>> Thx in advance!
>>
>> Ron
>>
>>
>>
>
>
> As we are PG users, on a PG list, we are gonna recommend PG,
> obviously. :-)
>
> Actually though, I recommend PG.
>
>
> > - The products that match with the most properties should be in the top
> > of the search results
>
>
> That kinda query is going to be really difficult, I think, regardless
> of what you use.  To find that you'll have to measure every product
> (all 5 million) and then sort the results.
>
>
> > enumerated types (CREATE TYPE propertyvalue AS ENUM ('option1',
> > 'option2', etc..)
>
> So, you have something like:
>
> CREATE TYPE colortype AS ENUM ('red', 'green', 'blue');
> CREATE TYPE sizetype AS ENUM ('small', 'medium', 'large');
>
> create table product
> (
>   id serial,
>   name text,
>   color colortype,
>   size  sizetype,
>...
> );
>
>
> I assume the problem is you don't want to index all 30 properties?
> That makes sense.
>
> > - It should be possible to search for products and provide properties
> > that the product SHOULD have, not must have.
>
> I don't understand this.  Say you have a sprocket in red and green.
> Do you want to search for:
>
> select * from product where name = 'sprocket' and (color = 'red' or
> color = 'green')
>
> Or do you want something else?  Does the user say they'd "prefer"
> blue, but will take whatever else you have?
>
> Do you search for some properties exactly and some "preferred"?
>
> Perhaps you could describe a little more how you want to query the
> database?  Or, maybe, what your user's are searching for?
>
> -Andy
>
>
Well, given that there are known limited attributes, this is the type of
application that really really suits a column oriented database, such as
Sybase IQ (now sold by SAP). Its a neat product that scales. Great
performance with drag'n'drop analytics.

Unless you can charm IQ out of SAP (it has been known to happen), you
might have to look at some other techniques

So consider some binary data representation
Red - 1 ( 0001)
Orange - 2 ( 0010)
Yellow - 4 ( 0100)
Green - 8 ( 1000)
Blue - 16 (0001 )
Indigo - 32 (0010 )
Violet - 64 (0100 )

This way, you can encode several colours in 1 value
Red or Green or Indigo = 1 + 8  + 32 = 41 = 0010 1001


Robin


--
Sent via pgsql-general mailing list (pgsql-general@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-general


-- 
Sent via pgsql-general mailing list (pgsql-general@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-general

Re: [GENERAL] Could use some advice on search architecture

[Robin]

bottom post
On 19/04/2014 12:46, R. Pasch wrote:

On 19-4-2014 9:38, Robin wrote:


Well, given that there are known limited attributes, this is the type 
of application that really really suits a column oriented database, 
such as Sybase IQ (now sold by SAP). Its a neat product that scales. 
Great performance with drag'n'drop analytics.


Unless you can charm IQ out of SAP (it has been known to happen), you 
might have to look at some other techniques


So consider some binary data representation
Red - 1 ( 0001)
Orange - 2 ( 0010)
Yellow - 4 ( 0100)
Green - 8 ( 1000)
Blue - 16 (0001 )
Indigo - 32 (0010 )
Violet - 64 (0100 )

This way, you can encode several colours in 1 value
Red or Green or Indigo = 1 + 8  + 32 = 41 = 0010 1001


Robin


I stopped reading when I heard the word "sold by SAP" ;-) This project 
is solely build with open-source and freely available software.


I've been thinking about using a binary data representation but didn't 
come to a solution to this specific problem quite yet. Per property of 
a product, only one bit would be 1 and the rest would be 0. What would 
a query look like to match all products that have a bit in the correct 
position?


Say for instance these are a couple records (and yes, property values 
can be null as well)


title, property1, property2, property3

product1,  0001,  0010, NULL
product2,  0100, 0100 , 0010 
product3, 0010 , 0010 , 0100 

Say that I would like to retrieve the products that either have 
property1 as 0010 , 1000 000 or  0001. Combined that would be 
0010 1001 and would have to match product1 and product3 as they both 
have their individual bit matching one of the bits being asked for. 
What would a where statement look like using this type of binary 
representation?


If that would be fairly simple to do and fast (most important factor) 
then I could do an OR construction on all property columns and have 
something count the amount of properties that actually matched. Is 
that something you can do with a binary operator of some sort as well? 
Count the amount of overlapping bits?


Say for instance I have a binary value of 0110 0101 and another binary 
value of 1100 0100, how could I found out how many bits matched? (in 
this case the number of matching bits would be 2)




I understand the reluctance to pay SAP-style rates, as a longtime DB 
user, I have learned some 'charm' techniques.


However, I poked around a bit for alternatives, as I do like the 
column-oriented approach, and found something called - /MonetDB / 
- it apparently has a column-store 
db kernel, and is open source - I suggest you have a look, if it does 
what it says on the label, then it looks like a find.


There is a discussion of bitmask-trickiness here also dealing with 
colours 



Robin

Re: [GENERAL] Could use some advice on search architecture

[Dorian Hoxha]

Postgresql has 2 column store, 1-in memory(cant remember the name) and
http://www.citusdata.com/blog/76-postgresql-columnar-store-for-analytics


On Sat, Apr 19, 2014 at 2:10 PM, Robin  wrote:

>  bottom post
> On 19/04/2014 12:46, R. Pasch wrote:
>
> On 19-4-2014 9:38, Robin wrote:
>
>
> Well, given that there are known limited attributes, this is the type of
> application that really really suits a column oriented database, such as
> Sybase IQ (now sold by SAP). Its a neat product that scales. Great
> performance with drag'n'drop analytics.
>
> Unless you can charm IQ out of SAP (it has been known to happen), you
> might have to look at some other techniques
>
> So consider some binary data representation
> Red - 1 ( 0001)
> Orange - 2 ( 0010)
> Yellow - 4 ( 0100)
> Green - 8 ( 1000)
> Blue - 16 (0001 )
> Indigo - 32 (0010 )
> Violet - 64 (0100 )
>
> This way, you can encode several colours in 1 value
> Red or Green or Indigo = 1 + 8  + 32 = 41 = 0010 1001
>
>
> Robin
>
>
>  I stopped reading when I heard the word "sold by SAP" ;-) This project is
> solely build with open-source and freely available software.
>
> I've been thinking about using a binary data representation but didn't
> come to a solution to this specific problem quite yet. Per property of a
> product, only one bit would be 1 and the rest would be 0. What would a
> query look like to match all products that have a bit in the correct
> position?
>
> Say for instance these are a couple records (and yes, property values can
> be null as well)
>
> title, property1, property2, property3
> 
> product1,  0001,  0010, NULL
> product2,  0100, 0100 , 0010 
> product3, 0010 , 0010 , 0100 
>
> Say that I would like to retrieve the products that either have property1
> as 0010 , 1000 000 or  0001. Combined that would be 0010 1001 and
> would have to match product1 and product3 as they both have their
> individual bit matching one of the bits being asked for. What would a where
> statement look like using this type of binary representation?
>
> If that would be fairly simple to do and fast (most important factor) then
> I could do an OR construction on all property columns and have something
> count the amount of properties that actually matched. Is that something you
> can do with a binary operator of some sort as well? Count the amount of
> overlapping bits?
>
> Say for instance I have a binary value of 0110 0101 and another binary
> value of 1100 0100, how could I found out how many bits matched? (in this
> case the number of matching bits would be 2)
>
>
> I understand the reluctance to pay SAP-style rates, as a longtime DB user,
> I have learned some 'charm' techniques.
>
> However, I poked around a bit for alternatives, as I do like the
> column-oriented approach, and found something called - *MonetDB 
> *-
> it apparently has a column-store db kernel, and is open source - I suggest
> you have a look, if it does what it says on the label, then it looks like a
> find.
>
> There is a discussion of bitmask-trickiness here also dealing with 
> colours
>
> Robin
> 
>
>

Re: [GENERAL] Could use some advice on search architecture

[Andy Colson]

On 04/19/2014 06:26 AM, Ron Pasch wrote:

 > - It should be possible to search for products and provide properties
 > that the product SHOULD have, not must have.


I don't understand this.  Say you have a sprocket in red and green. Do you want 
to search for:

select * from product where name = 'sprocket' and (color = 'red' or color = 
'green')

Or do you want something else?  Does the user say they'd "prefer" blue, but 
will take whatever else you have?

Do you search for some properties exactly and some "preferred"?

Perhaps you could describe a little more how you want to query the database?  
Or, maybe, what your user's are searching for?

-Andy




Yes, the user can prefer certain properties and the products that match most of 
the properties should be in the top of the results, but if a product doesn't 
match all of them but just some of them, they should still be returned, but 
lower in the results.

I'm seriously wondering if doing this solely with postgres is even possible without 
having long execution times. I've done some tests with 5 million records and just doing 
the "or" construction you mentioned above, which resulted in 600 to 900 ms 
queries and returning only those records of which all properties match at least one 
selected value.

I was thinking that perhaps using a search engine like lucene or sphinx would 
be more appropriate, but then I wonder what I would exactly be indexing and how 
I would be querying that, but that's a question for a different mailing list ;-)


Please keep the list cc'd, so others can help as well.

Yeah, doing a bunch of or's is gonna have to test all 5 million products.

I wonder if there is a way we can treat this like a two step process.

1) cut down the number of products

2) sort them by #matches, popularity, etc

You've talked about #2, but how about #1.  Is there any way to either include or exclude 
a product?  Users don't just ask for red, they ask for "tires (maybe red)".  
Not all 5 million products are tires, right?

-Andy



--
Sent via pgsql-general mailing list (pgsql-general@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-general

Re: [GENERAL] Could use some advice on search architecture

[Marc Mamin]

>On 04/19/2014 06:26 AM, Ron Pasch wrote:
>>  > - It should be possible to search for products and provide properties
>>  > that the product SHOULD have, not must have.
>>>
>>> I don't understand this.  Say you have a sprocket in red and green. Do you 
>>> want to search for:
>>>
>>> select * from product where name = 'sprocket' and (color = 'red' or color = 
>>> 'green')
>>>
>>> Or do you want something else?  Does the user say they'd "prefer" blue, but 
>>> will take whatever else you have?
>>>
>>> Do you search for some properties exactly and some "preferred"?
>>>
>>> Perhaps you could describe a little more how you want to query the 
>>> database?  Or, maybe, what your user's are searching for?
>>>
>>> -Andy
>>>
>>
>> Yes, the user can prefer certain properties and the products that match most 
>> of the properties should be in the top of the results, but if a product 
>> doesn't match all of them but just some of them, they should still be 
>> returned, but lower in the results.
>>
>> I'm seriously wondering if doing this solely with postgres is even possible 
>> without having long execution times. I've done some tests with 5 million 
>> records and just doing the "or" construction you mentioned above, which 
>> resulted in 600 to 900 ms queries and returning only those records of which 
>> all properties match at least one selected value.

 I don't think that OR clauses are the right way as the aim is to count how 
many attributes do match the search.
 basically a standard approach would look like:
 
 SELECT pID, sum(match) as matches FROM
 (
 selct pID, 1 as match from Products where color ='pink'
 UNION ALL
 selct pID, 1 as match from Products where size ='XXL'
 ...
 )foo
GROUP BY pID order by matches DESC

How many distinct attributes are involved ? ( 15 colors + 9 sizes + )

Marc

>>
>> I was thinking that perhaps using a search engine like lucene or sphinx 
>> would be more appropriate, but then I wonder what I would exactly be 
>> indexing and how I would be querying that, but that's a question for a 
>> different mailing list ;-)
>
>Please keep the list cc'd, so others can help as well.
>
>Yeah, doing a bunch of or's is gonna have to test all 5 million products.
>
>I wonder if there is a way we can treat this like a two step process.
>
>1) cut down the number of products
>
>2) sort them by #matches, popularity, etc
>
>You've talked about #2, but how about #1.  Is there any way to either include 
>or exclude a product?  Users don't just ask for red, they ask for "tires 
>(maybe red)".  Not all 5 million products are tires, right?
>
>-Andy


-- 
Sent via pgsql-general mailing list (pgsql-general@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-general

[GENERAL] Disable an index temporarily

[Torsten Förtsch]

Hi,

an index can be INVALID (pg_index.indisvalid=false).

I want to temporarily disable an index so that it won't be used to
access data but will still be updated.

Can I simply set pg_index.indisvalid=false and later turn it true again?

Thanks,
Torsten


-- 
Sent via pgsql-general mailing list (pgsql-general@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-general

Re: [GENERAL] Could use some advice on search architecture

[Robin]

Because this is a topic that interests me I have done some digging.

MonetDB is a proper column-store DBMS. It 
is used on some decent sized projects, several of which are EU-funded.


Digging a bit deeper I have discovered that a PostgreSQL Foreign Data 
Wrapper for MonetDB has been created - monetdb_fdw.


The fdw is written up here 



There is a video that shows what happens when a query is executed in 
PostgreSQL and MonetDB


The video shows an analytical query being processed

1. Using PostgreSQL - 177 seconds
2. Using MonetDB - 8 seconds
3. Using a remote MonetDB server through MonetDB FDW - 1 second


I think its worth investigating further

Robin St.Clair

[GENERAL] Re: [PERFORM] Hot standby 9.2.1 PANIC: WAL contains references to invalid pages

[Sergey Konoplev]

On Fri, Apr 18, 2014 at 1:23 AM, Vishalakshi Navaneethakrishnan
 wrote:
> if i change the wal level as archive, then this problem will go..? We are
> just using warm stand by. so shall we change the wal_level as archive..? Can
> you please reply this mail as soon as possible?

AFAIK, the problem appears when hot_standby is set on, so you need to
turn it off. Also, take a look at the link below:

http://www.databasesoup.com/2013/12/why-you-need-to-apply-todays-update.html

-- 
Kind regards,
Sergey Konoplev
PostgreSQL Consultant and DBA

http://www.linkedin.com/in/grayhemp
+1 (415) 867-9984, +7 (901) 903-0499, +7 (988) 888-1979
gray...@gmail.com


-- 
Sent via pgsql-general mailing list (pgsql-general@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-general

Re: [GENERAL] Could use some advice on search architecture

[Jov]

the other is named imcs.
imcs is mainly a memory database,it is very fast for olap,because of multi
threads parallel query plan and column storage.for billions of data,most
group by like querys return within 2s.
we use it for several weeks and happy for the performance.

jov
在 2014-4-19 下午8:27，"Dorian Hoxha" 写道：

> Postgresql has 2 column store, 1-in memory(cant remember the name) and
> http://www.citusdata.com/blog/76-postgresql-columnar-store-for-analytics
>
>
> On Sat, Apr 19, 2014 at 2:10 PM, Robin  wrote:
>
>>  bottom post
>> On 19/04/2014 12:46, R. Pasch wrote:
>>
>> On 19-4-2014 9:38, Robin wrote:
>>
>>
>> Well, given that there are known limited attributes, this is the type of
>> application that really really suits a column oriented database, such as
>> Sybase IQ (now sold by SAP). Its a neat product that scales. Great
>> performance with drag'n'drop analytics.
>>
>> Unless you can charm IQ out of SAP (it has been known to happen), you
>> might have to look at some other techniques
>>
>> So consider some binary data representation
>> Red - 1 ( 0001)
>> Orange - 2 ( 0010)
>> Yellow - 4 ( 0100)
>> Green - 8 ( 1000)
>> Blue - 16 (0001 )
>> Indigo - 32 (0010 )
>> Violet - 64 (0100 )
>>
>> This way, you can encode several colours in 1 value
>> Red or Green or Indigo = 1 + 8  + 32 = 41 = 0010 1001
>>
>>
>> Robin
>>
>>
>>  I stopped reading when I heard the word "sold by SAP" ;-) This project
>> is solely build with open-source and freely available software.
>>
>> I've been thinking about using a binary data representation but didn't
>> come to a solution to this specific problem quite yet. Per property of a
>> product, only one bit would be 1 and the rest would be 0. What would a
>> query look like to match all products that have a bit in the correct
>> position?
>>
>> Say for instance these are a couple records (and yes, property values can
>> be null as well)
>>
>> title, property1, property2, property3
>> 
>> product1,  0001,  0010, NULL
>> product2,  0100, 0100 , 0010 
>> product3, 0010 , 0010 , 0100 
>>
>> Say that I would like to retrieve the products that either have property1
>> as 0010 , 1000 000 or  0001. Combined that would be 0010 1001 and
>> would have to match product1 and product3 as they both have their
>> individual bit matching one of the bits being asked for. What would a where
>> statement look like using this type of binary representation?
>>
>> If that would be fairly simple to do and fast (most important factor)
>> then I could do an OR construction on all property columns and have
>> something count the amount of properties that actually matched. Is that
>> something you can do with a binary operator of some sort as well? Count the
>> amount of overlapping bits?
>>
>> Say for instance I have a binary value of 0110 0101 and another binary
>> value of 1100 0100, how could I found out how many bits matched? (in this
>> case the number of matching bits would be 2)
>>
>>
>> I understand the reluctance to pay SAP-style rates, as a longtime DB
>> user, I have learned some 'charm' techniques.
>>
>> However, I poked around a bit for alternatives, as I do like the
>> column-oriented approach, and found something called - *MonetDB 
>> *-
>> it apparently has a column-store db kernel, and is open source - I suggest
>> you have a look, if it does what it says on the label, then it looks like a
>> find.
>>
>> There is a discussion of bitmask-trickiness here also dealing with
>> colours
>>
>> Robin
>> 
>>
>>
>

Re: [GENERAL] Disable an index temporarily

[Sergey Konoplev]

On Apr 19, 2014 1:53 PM, "Torsten Förtsch"  wrote:
>
> Hi,
>
> an index can be INVALID (pg_index.indisvalid=false).
>
> I want to temporarily disable an index so that it won't be used to
> access data but will still be updated.
>
> Can I simply set pg_index.indisvalid=false and later turn it true again?

It works on a quick test, but I'm not sure how safe it is.

If you need to test a query without the index use a transaction:

Begin;
Drop index ...;
Explain ... select ...;
Rollback;

>
> Thanks,
> Torsten
>
>
> --
> Sent via pgsql-general mailing list (pgsql-general@postgresql.org)
> To make changes to your subscription:
> http://www.postgresql.org/mailpref/pgsql-general