Thread: Plans for partitioning of inheriting tables

Hi

Up to version 17, partitioning of tables inheriting from other tables  
is not possible.
> psql:../code_files/data_storage/PostgreSQL/tables/TOPO_FILES.pg_sql:68:  
> ERROR:  no se puede crear una tabla particionada como hija de herencia

Are there plans to support this in the future? I could not find any  
hint in the documentation or in  
https://wiki.postgresql.org/wiki/Development_information.

Kind regards

Thiemo

On 10/24/24 12:47 PM, thiemo@gelassene-pferde.biz wrote:
> Hi
> 
> Up to version 17, partitioning of tables inheriting from other tables is 
> not possible.
>> psql:../code_files/data_storage/PostgreSQL/tables/TOPO_FILES.pg_sql:68: ERROR:  no se puede crear una tabla
particionadacomo hija de herencia
 
> 
> Are there plans to support this in the future? I could not find any hint 
> in the documentation or in 
> https://wiki.postgresql.org/wiki/Development_information.

1) Have you looked at?:

https://www.postgresql.org/docs/current/ddl-partitioning.html#DDL-PARTITIONING-USING-INHERITANCE

2) Provide the SQL you ran that got the above error.

> 
> Kind regards
> 
> Thiemo
> 
> 
> 

-- 
Adrian Klaver
adrian.klaver@aklaver.com

On Thursday, October 24, 2024, <thiemo@gelassene-pferde.biz> wrote:

Up to version 17, partitioning of tables inheriting from other tables is not possible.

psql:../code_files/data_storage/PostgreSQL/tables/TOPO_FILES.pg_sql:68: ERROR:  no se puede crear una tabla particionada como hija de herencia

Are there plans to support this in the future? I could not find any hint in the documentation or in https://wiki.postgresql.org/wiki/Development_information.

Thanks for taking this up.

24.10.2024 22:44:11 Adrian Klaver <adrian.klaver@aklaver.com>:

> 
> 1) Have you looked at?:
> 
> https://www.postgresql.org/docs/current/ddl-partitioning.html#DDL-PARTITIONING-USING-INHERITANCE

I do not feel it applies to my case. I tried to create a partitioned table that inherits columns from a base table. The
documentationyou provided the URL seems to speak of realising partitioning by using inheritance.
 

> 
> 2) Provide the SQL you ran that got the above error?


https://sourceforge.net/p/treintaytres/code/HEAD/tree/trunk/code_files/data_storage/PostgreSQL/tables/TEMPLATE_TECH.pg_sql

24.10.2024 22:58:39 David G. Johnston <david.g.johnston@gmail.com>:

My impression of things is that directly using “inherit” for table creation is considered deprecated at this point.  No one has interest in expanding on the feature nor even recommends it be used in new development.  That particular unique feature of PostgreSQL hasn’t caught on.

David J.
 

Thanks for sharing your experience. I wonder if this is the general take on inheritance for spreading common attributes throughout a database.

On 10/24/24 22:33, Thiemo Kellner wrote:
> Thanks for taking this up.
> 
> 24.10.2024 22:44:11 Adrian Klaver <adrian.klaver@aklaver.com>:
> 
>>
>> 1) Have you looked at?:
>>
>> https://www.postgresql.org/docs/current/ddl-partitioning.html#DDL-PARTITIONING-USING-INHERITANCE
> 
> I do not feel it applies to my case. I tried to create a partitioned table that inherits columns from a base table.
Thedocumentation you provided the URL seems to speak of realising partitioning by using inheritance.
 

This needs a code example to go any further.

> 
>>
>> 2) Provide the SQL you ran that got the above error?
> 
>
https://sourceforge.net/p/treintaytres/code/HEAD/tree/trunk/code_files/data_storage/PostgreSQL/tables/TEMPLATE_TECH.pg_sql
> 
> 

-- 
Adrian Klaver
adrian.klaver@aklaver.com

I do not feel it applies to my case. I tried to create a partitioned table that inherits columns from a base table. The documentation you provided the URL seems to speak of realising partitioning by using inheritance.

This needs a code example to go any further.

Sorry, my bad. I posted the URL of the table that is inherited from. The recepient is https://sourceforge.net/p/treintaytres/code/HEAD/tree/trunk/code_files/data_storage/PostgreSQL/tables/TOPO_FILES.pg_sqlcreate table if not exists TOPO_FILES (

     SOURCE_ID          uuid        constraint TOPO_FILES␟FK_01            references SOURCES (ID)            match full        not null    ,FILE_NAME          text        not null    ,TILE               raster        not null    ,FILE_CREATION_PIT  timestamp(6) with time zone        not null    ,FILE_HASH          text        not null    ,constraint TOPO_FILES␟PK primary key (ID)    ,constraint TOPO_FILES␟UQ unique (SOURCE_ID                                     ,FILE_NAME)
)
inherits(TEMPLATE_TECH);
-- partition by hash (source_id); --NOTE Up to PG 17, partitioning with inheriting table is not possible.


The spender table is https://sourceforge.net/p/treintaytres/code/HEAD/tree/trunk/code_files/data_storage/PostgreSQL/tables/TEMPLATE_TECH.pg_sql

create table if not exists TEMPLATE_TECH (     ID                 uuid        constraint TEMPLATE_TECH␟PK primary key        not null        default gen_random_uuid()    ,ENTRY_PIT          timestamp(6) with time zone        not null        default clock_timestamp()
);

I do not feel it applies to my case. I tried to create a partitioned table that inherits columns from a base table. The documentation you provided the URL seems to speak of realising partitioning by using inheritance.

This needs a code example to go any further.

Sorry, my bad. I posted the URL of the table that is inherited from. The recepient is https://sourceforge.net/p/treintaytres/code/HEAD/tree/trunk/code_files/data_storage/PostgreSQL/tables/TOPO_FILES.pg_sqlcreate table if not exists TOPO_FILES (

     SOURCE_ID          uuid        constraint TOPO_FILES␟FK_01            references SOURCES (ID)            match full        not null    ,FILE_NAME          text        not null    ,TILE               raster        not null    ,FILE_CREATION_PIT  timestamp(6) with time zone        not null    ,FILE_HASH          text        not null    ,constraint TOPO_FILES␟PK primary key (ID)    ,constraint TOPO_FILES␟UQ unique (SOURCE_ID                                     ,FILE_NAME)
)
inherits(TEMPLATE_TECH);
-- partition by hash (source_id); --NOTE Up to PG 17, partitioning with inheriting table is not possible.


The spender table is https://sourceforge.net/p/treintaytres/code/HEAD/tree/trunk/code_files/data_storage/PostgreSQL/tables/TEMPLATE_TECH.pg_sql

create table if not exists TEMPLATE_TECH (     ID                 uuid        constraint TEMPLATE_TECH␟PK primary key        not null        default gen_random_uuid()    ,ENTRY_PIT          timestamp(6) with time zone        not null        default clock_timestamp()
);

On 10/25/24 11:47, Thiemo Kellner wrote:
> 
> Am 25.10.2024 um 17:57 schrieb Adrian Klaver:
>>
>>> I do not feel it applies to my case. I tried to create a partitioned 
>>> table that inherits columns from a base table. The documentation you 
>>> provided the URL seems to speak of realising partitioning by using 
>>> inheritance.
>>
>> This needs a code example to go any further.
> 
> Sorry, my bad. I posted the URL of the table that is inherited from. The 
> recepient is 
>
https://sourceforge.net/p/treintaytres/code/HEAD/tree/trunk/code_files/data_storage/PostgreSQL/tables/TOPO_FILES.pg_sqlcreate
tableif not exists TOPO_FILES (
 
> 
>       SOURCE_ID          uuid
>          constraint TOPO_FILES␟FK_01
>              references SOURCES (ID)
>              match full
>          not null
>      ,FILE_NAME          text
>          not null
>      ,TILE               raster
>          not null
>      ,FILE_CREATION_PIT  timestamp(6) with time zone
>          not null
>      ,FILE_HASH          text
>          not null
>      ,constraint TOPO_FILES␟PK primary key (ID)
>      ,constraint TOPO_FILES␟UQ unique (SOURCE_ID
>                                       ,FILE_NAME)
> )
> inherits(TEMPLATE_TECH);
> -- partition by hash (source_id); --NOTE Up to PG 17, partitioning with inheriting table is not possible.

It is just not the way you want to do it, see:

https://www.postgresql.org/docs/current/ddl-partitioning.html#DDL-PARTITIONING-USING-INHERITANCE


> 
> 
> The spender table
ishttps://sourceforge.net/p/treintaytres/code/HEAD/tree/trunk/code_files/data_storage/PostgreSQL/tables/TEMPLATE_TECH.pg_sql
> 
> create table if not exists TEMPLATE_TECH (
>       ID                 uuid
>          constraint TEMPLATE_TECH␟PK primary key
>          not null
>          default gen_random_uuid()
>      ,ENTRY_PIT          timestamp(6) with time zone
>          not null
>          default clock_timestamp()
> );
> 
> 

-- 
Adrian Klaver
adrian.klaver@aklaver.com

Adrian Klaver <adrian.klaver@aklaver.com> escribió:


> It is just not the way you want to do it, see:
>
> https://www.postgresql.org/docs/current/ddl-partitioning.html#DDL-PARTITIONING-USING-INHERITANCE

Thanks for your patience. Maybe I am not clever enough to understand  
you. I shall try to explain what I try to do.

In my project, I have several tables. Each table has some basic  
technical attributes. For the time being, those are the surrogate key  
(ID) and a timestamp (ENTRY_PIT) to track the point in time when a  
record was inserted into the table. To improve consistency and reduce  
effort, I created a template table those attributes get inherited from  
by all other tables, e.g. TOPO_FILES. TOPO_FILES can contain  
GeoTIFF/raster data from different sources. For ease of data  
management, e.g. wipe all the data of one source, I tried to partition  
it by SOURCE_ID. And there the error rises that it is not possible to  
partition a table that is an heir of another table.

I feel, you are trying to make me partition TOPO_SOURCES by using  
inheritance, but I cannot see... now I do see how I could achieve my  
desires. However, there pop up questions in my mind.

To me, it seems, that partitioning using inheritance will not reduce  
maintenance but greatly increase it. It feels to me very much that I  
build manually with inheritance, what is done with the partitioning  
clause. Am I mistaken?

In the description, there is the statement that instead of triggers,  
one could use rules. I am quite sure that, quite a while ago, I was  
advised in one of the mailing lists against the use of rules other  
than for inserts as the workings of update and delete rules are almost  
impenetrable. For me, at least, they were. Are my memories wrong about  
that?

Is there experience on the efficiency/speed comparing partitioning  
with inheritance using triggers/rules and using the declarative way? I  
don't think that partition speed is an issue in my case, as I have  
fairly few records that are in themselves rather big.

Remarks to the documentation:
- There are examples for the insert path. However, not for the update  
or delete path. I feel, that those tend to be the more complex ones,  
especially if my memory is correct about the advice to avoid update  
and delete rules.
-  
https://www.postgresql.org/docs/current/ddl-partitioning.html#DDL-PARTITIONING-INHERITANCE-MAINTENANCE misses out on a
sentencenot to forget to adapt the  
 
triggers/rules.

Kind regards

Thiemo

On Thursday, October 24, 2024, <thiemo@gelassene-pferde.biz> wrote:

Up to version 17, partitioning of tables inheriting from other tables is not possible.

psql:../code_files/data_storage/PostgreSQL/tables/TOPO_FILES.pg_sql:68: ERROR:  no se puede crear una tabla particionada como hija de herencia

Are there plans to support this in the future? I could not find any hint in the documentation or in https://wiki.postgresql.org/wiki/Development_information.

My impression of things is that directly using “inherit” for table creation is considered deprecated at this point.  No one has interest in expanding on the feature nor even recommends it be used in new development.  That particular unique feature of PostgreSQL hasn’t caught on.

Hi, opinions vary, IMHO inheritance it is a nice feature to have especially in multi-tenant situation where tenants represent a division or subsidiary rather than a completely foreign entity which should live in total isolation, plus the ability to have data on the top owning or managing organization. IMHO nothing beats inheritance in fitting to the above model. Partitioning comes close but partitioned tables cannot have any data on their own. There are workarounds of course to that, but they don't fit like a glove. But again I have not tested in heavy xactional envs TBT, I am just saying the feature is handy for many applications and models. I use it personally in my company and love it. Could I do without it? of course, but it would be ugly.

David J.

 

On 11/1/24 01:41, thiemo@gelassene-pferde.biz wrote:
> 
> Adrian Klaver <adrian.klaver@aklaver.com> escribió:
> 
> 
>> It is just not the way you want to do it, see:
>>
>> https://www.postgresql.org/docs/current/ddl-partitioning.html#DDL-PARTITIONING-USING-INHERITANCE
> 
> Thanks for your patience. Maybe I am not clever enough to understand 
> you. I shall try to explain what I try to do.
> 
> In my project, I have several tables. Each table has some basic 
> technical attributes. For the time being, those are the surrogate key 
> (ID) and a timestamp (ENTRY_PIT) to track the point in time when a 
> record was inserted into the table. To improve consistency and reduce 
> effort, I created a template table those attributes get inherited from 
> by all other tables, e.g. TOPO_FILES. TOPO_FILES can contain 
> GeoTIFF/raster data from different sources. For ease of data management, 
> e.g. wipe all the data of one source, I tried to partition it by 
> SOURCE_ID. And there the error rises that it is not possible to 
> partition a table that is an heir of another table.
> 
> I feel, you are trying to make me partition TOPO_SOURCES by using 
> inheritance, but I cannot see... now I do see how I could achieve my 
> desires. However, there pop up questions in my mind.
> 
> To me, it seems, that partitioning using inheritance will not reduce 
> maintenance but greatly increase it. It feels to me very much that I 
> build manually with inheritance, what is done with the partitioning 
> clause. Am I mistaken?

 From here:

https://www.postgresql.org/docs/current/ddl-partitioning.html#DDL-PARTITIONING-DECLARATIVE

5.12.2.3. Limitations

"Individual partitions are linked to their partitioned table using 
inheritance behind-the-scenes. However, it is not possible to use all of 
the generic features of inheritance with declaratively partitioned 
tables or their partitions, as discussed below. Notably, a partition 
cannot have any parents other than the partitioned table it is a 
partition of, nor can a table inherit from both a partitioned table and 
a regular table. That means partitioned tables and their partitions 
never share an inheritance hierarchy with regular tables."


Changing that would count as a major change. Even if you where to 
convince the developers to make the change the earliest it would 
released would be with the next major release in Fall of 2025. That 
assumes you can convince then early enough or at all. What I getting at 
is that you need to start thinking of another way of doing this if this 
is a current project. The choices are:

1) Declarative partitioning, where you cannot have your partition parent 
inherit from another table.

2) Partition by inheritance where you build the structure manually.



> 
> In the description, there is the statement that instead of triggers, one 
> could use rules. I am quite sure that, quite a while ago, I was advised 
> in one of the mailing lists against the use of rules other than for 
> inserts as the workings of update and delete rules are almost 
> impenetrable. For me, at least, they were. Are my memories wrong about 
> that?

Yes, I would stay away from rules. They are included in the 
documentation for completeness. You have enough on your plate without 
trying to figure out what rules do.

> 
> Is there experience on the efficiency/speed comparing partitioning with 
> inheritance using triggers/rules and using the declarative way? I don't 
> think that partition speed is an issue in my case, as I have fairly few 
> records that are in themselves rather big.

Hard to say without some firm numbers and/or testing.

Also this "... I have fairly few records that are in themselves rather 
big" could use some explanation. In other words what makes you think 
that partitioning is the answer to this issue?

> 
> Remarks to the documentation:
> - There are examples for the insert path. However, not for the update or 
> delete path. I feel, that those tend to be the more complex ones, 
> especially if my memory is correct about the advice to avoid update and 
> delete rules.


 From the docs:

"The schemes shown here assume that the values of a row's key column(s) 
never change, or at least do not change enough to require it to move to 
another partition. An UPDATE that attempts to do that will fail because 
of the CHECK constraints. If you need to handle such cases, you can put 
suitable update triggers on the child tables, but it makes management of 
the structure much more complicated."

So yes, they would be more complicated as you are looking at possibly 
changing tables.

Personally, I think you are heading to declarative partitioning. Either 
via your own scripts or something like 
pg_partman(https://github.com/pgpartman/pg_partman).


> - 
> https://www.postgresql.org/docs/current/ddl-partitioning.html#DDL-PARTITIONING-INHERITANCE-MAINTENANCE misses out on
asentence not to forget to adapt the triggers/rules.
 
> 
> Kind regards
> 
> Thiemo
> 
> 
> 

-- 
Adrian Klaver
adrian.klaver@aklaver.com

Adrian Klaver <adrian.klaver@aklaver.com> escribió:

> Changing that would count as a major change. Even if you where to  
> convince the developers to make the change the earliest it would  
> released would be with the next major release in Fall of 2025. That  
> assumes you can convince then early enough or at all.

I was not trying to convince anyone to do anything about the  
implementation of declarative partitioning. I have been just curious  
if there were plans. If I have raised the impression of the former, I  
am sorry.

> What I getting at is that you need to start thinking of another way  
> of doing this if this is a current project. The choices are:
>
> 1) Declarative partitioning, where you cannot have your partition  
> parent inherit from another table.
>
> 2) Partition by inheritance where you build the structure manually.

I very much agree. Shying the effort involved for 2), I still tend to  
1). I could break the inheritance pattern by explicitly putting the  
technical attributes into partitioned tables. My self, I probably  
won't use more than one source, but others might have several source  
for comparison or whatever.

>> Is there experience on the efficiency/speed comparing partitioning  
>> with inheritance using triggers/rules and using the declarative  
>> way? I don't think that partition speed is an issue in my case, as  
>> I have fairly few records that are in themselves rather big.
>
> Hard to say without some firm numbers and/or testing.

Sure, I was hoping those test would have been done some day. But in  
the end, to me, it is not important.

> Also this "... I have fairly few records that are in themselves  
> rather big" could use some explanation. In other words what makes  
> you think that partitioning is the answer to this issue?

I was not thinking that partitioning was the answer to a performance  
problem. Partitioning might be an answer to the maintenance of  
records, specifically if entire sources are affected. The size of the  
tif files to get loaded into the raster attribute TILE range from 112  
kB to 32 MB. I am complete unaware of the inner storing mechanisms of  
raster in PostGIS, but on first sight, it seems that the rest of a  
records of TOPO_FILES is negligible compared to the TILE. The total  
number of files to be loaded in my case are 3273, even though that  
only encompasses a small part of the world, I do not think, the latter  
would surpass 100000 records. Not much for a database table, afaik. I  
mean to say that I believe that loading that much data into one field  
will take much more time than runtime difference of  
trigger/rules/declarative partitioning solutions would to sort the  
data into the correct partition.

On 11/1/24 10:21 AM, thiemo@gelassene-pferde.biz wrote:
> 
> Adrian Klaver <adrian.klaver@aklaver.com> escribió:
> 
>> Changing that would count as a major change. Even if you where to 
>> convince the developers to make the change the earliest it would 
>> released would be with the next major release in Fall of 2025. That 
>> assumes you can convince then early enough or at all.
> 
> I was not trying to convince anyone to do anything about the 
> implementation of declarative partitioning. I have been just curious if 
> there were plans. If I have raised the impression of the former, I am 
> sorry.
Even if there where plans, any changes would happen in the future and 
would not be help the now problem.


>>> Is there experience on the efficiency/speed comparing partitioning 
>>> with inheritance using triggers/rules and using the declarative way? 
>>> I don't think that partition speed is an issue in my case, as I have 
>>> fairly few records that are in themselves rather big.
>>
>> Hard to say without some firm numbers and/or testing.
> 
> Sure, I was hoping those test would have been done some day. But in the 
> end, to me, it is not important.

That is contradicted by your statement below:

"I mean to say that I believe that loading that much data into one field 
will take much more time than runtime difference of 
trigger/rules/declarative partitioning solutions would to sort the data 
into the correct partition."

Either performance is important or it is not.

If TILE is referring to the same thing you are dealing with in related 
question on psycopg list then you are talking about bytea storage. You 
should take a look at:

https://www.postgresql.org/docs/current/storage-toast.html

In any case assuming you are not entering/reading/updating all the bytea 
data at one time then you are looking at fetching only that bytea data 
that are filtered by other attributes of the rows. I would strongly 
suggest running some tests on a single table with the data and see if 
you can live with the performance results before complicating things 
with partitioning.

> 
>> Also this "... I have fairly few records that are in themselves rather 
>> big" could use some explanation. In other words what makes you think 
>> that partitioning is the answer to this issue?
> 
> I was not thinking that partitioning was the answer to a performance 
> problem. Partitioning might be an answer to the maintenance of records, 
> specifically if entire sources are affected. The size of the tif files 
> to get loaded into the raster attribute TILE range from 112 kB to 32 MB. 
> I am complete unaware of the inner storing mechanisms of raster in 
> PostGIS, but on first sight, it seems that the rest of a records of 
> TOPO_FILES is negligible compared to the TILE. The total number of files 
> to be loaded in my case are 3273, even though that only encompasses a 
> small part of the world, I do not think, the latter would surpass 100000 
> records. Not much for a database table, afaik. I mean to say that I 
> believe that loading that much data into one field will take much more 
> time than runtime difference of trigger/rules/declarative partitioning 
> solutions would to sort the data into the correct partition.
> 

-- 
Adrian Klaver
adrian.klaver@aklaver.com

Adrian Klaver <adrian.klaver@aklaver.com> escribió:

> Even if there where plans, any changes would happen in the future  
> and would not be help the now problem.

Yes and no. I can live without the partitioning, as I do not intend to  
load data from more than one source. Other might. But until others  
want to load data from different sources, a comment in the source  
might do that partitioning of inheriting tables will be supported in  
the future. But, that is an academic point now.

> That is contradicted by your statement below:
>
> Either performance is important or it is not.

Not quite. If the performance penalty by suboptimal choice in  
partitioning does not matter in the current project because the  
raster/bytea stuff does affect performance much more, it does not mean  
that I cannot work on other project where it can matter. And even if  
the latter is not the case, I can be just curious about it.

> If TILE is referring to the same thing you are dealing with in  
> related question on psycopg list then you are talking about bytea  
> storage. You should take a look at:
>
> https://www.postgresql.org/docs/current/storage-toast.html

Indeed, it does. Thanks for the hint.

Thanks, I shall have a look into it. I was under the assumption the the create table like would create no more than a structural copy.

Torsten Förtsch <tfoertsch123@gmail.com> escribió:

Thiemo,

 

it looks to me like you are using inheritance just to make sure your SOURCES and TOPO_FILES tables have some common columns. If you are not actually querying the TEMPLATE_TECH table and expect to see all the rows from the other 2 tables in that one table combined, then you could use CREATE TABLE (LIKE ...) instead of inheritance. That way your "child" tables would become normal tables and you could use declarative partitioning on them.

 

Even if you are querying the TEMPLATE_TECH table, you could still do that by turning the TEMPLATE_TECH table into a view which performs a UNION ALL over the other tables.

On 11/1/24 12:16, thiemo@gelassene-pferde.biz wrote:
> Thanks, I shall have a look into it. I was under the assumption the the 
> create table like would create no more than a structural copy.

Not sure what you mean by structural copy, but the table created by 
CREATE TABLE LIKE will not have any association with the table it was 
created from.

https://www.postgresql.org/docs/current/sql-createtable.html

"Unlike INHERITS, the new table and original table are completely 
decoupled after creation is complete. Changes to the original table will 
not be applied to the new table, and it is not possible to include data 
of the new table in scans of the original table."

> 
> Torsten Förtsch <tfoertsch123@gmail.com <mailto:tfoertsch123@gmail.com>> 
> escribió:
> 
>> Thiemo,
>> it looks to me like you are using inheritance just to make sure your 
>> SOURCES and TOPO_FILES tables have some common columns. If you are not 
>> actually querying the TEMPLATE_TECH table and expect to see all the 
>> rows from the other 2 tables in that one table combined, then you 
>> could use CREATE TABLE (LIKE ...) instead of inheritance. That way 
>> your "child" tables would become normal tables and you could use 
>> declarative partitioning on them.
>> Even if you are querying the TEMPLATE_TECH table, you could still do 
>> that by turning the TEMPLATE_TECH table into a view which performs a 
>> UNION ALL over the other tables.
> 
> 

-- 
Adrian Klaver
adrian.klaver@aklaver.com

It looks to me basically to be a "create table A as select * from B where false".

01.11.2024 20:38:15 Adrian Klaver <adrian.klaver@aklaver.com>:

> On 11/1/24 12:16, thiemo@gelassene-pferde.biz wrote:
>> Thanks, I shall have a look into it. I was under the assumption the the create table like would create no more than
astructural copy. 
>
> Not sure what you mean by structural copy, but the table created by CREATE TABLE LIKE will not have any association
withthe table it was created from. 
>
> https://www.postgresql.org/docs/current/sql-createtable.html
>
> "Unlike INHERITS, the new table and original table are completely decoupled after creation is complete. Changes to
theoriginal table will not be applied to the new table, and it is not possible to include data of the new table in
scansof the original table." 
>
>> Torsten Förtsch <tfoertsch123@gmail.com <mailto:tfoertsch123@gmail.com>> escribió:
>> Thiemo,
>>> it looks to me like you are using inheritance just to make sure your SOURCES and TOPO_FILES tables have some common
columns.If you are not actually querying the TEMPLATE_TECH table and expect to see all the rows from the other 2 tables
inthat one table combined, then you could use CREATE TABLE (LIKE ...) instead of inheritance. That way your "child"
tableswould become normal tables and you could use declarative partitioning on them. 
>>> Even if you are querying the TEMPLATE_TECH table, you could still do that by turning the TEMPLATE_TECH table into a
viewwhich performs a UNION ALL over the other tables. 
>>
>
> --
> Adrian Klaver
> adrian.klaver@aklaver.com

On 11/1/24 13:47, Thiemo Kellner wrote:
> It looks to me basically to be a "create table A as select * from B where false".

No it more capable then that.

CREATE TABLE <some_tbl> AS <some_other_tbl> is bare bones, you get the 
column names, types and data(or not) and that is it.

CREATE TABLE <some_tbl> LIKE <some_other_tbl> has  like_option which 
allows to transfer over more attributes of the table, for example 
defaults, constraints, indexes, etc.

See

https://www.postgresql.org/docs/current/sql-createtable.html

LIKE source_table [ like_option ... ]


> 
> 01.11.2024 20:38:15 Adrian Klaver <adrian.klaver@aklaver.com>:
> 
>> On 11/1/24 12:16, thiemo@gelassene-pferde.biz wrote:
>>> Thanks, I shall have a look into it. I was under the assumption the the create table like would create no more than
astructural copy.
 
>>
>> Not sure what you mean by structural copy, but the table created by CREATE TABLE LIKE will not have any association
withthe table it was created from.
 
>>
>> https://www.postgresql.org/docs/current/sql-createtable.html
>>
>> "Unlike INHERITS, the new table and original table are completely decoupled after creation is complete. Changes to
theoriginal table will not be applied to the new table, and it is not possible to include data of the new table in
scansof the original table."
 
>>
>>> Torsten Förtsch <tfoertsch123@gmail.com <mailto:tfoertsch123@gmail.com>> escribió:
>>> Thiemo,
>>>> it looks to me like you are using inheritance just to make sure your SOURCES and TOPO_FILES tables have some
commoncolumns. If you are not actually querying the TEMPLATE_TECH table and expect to see all the rows from the other 2
tablesin that one table combined, then you could use CREATE TABLE (LIKE ...) instead of inheritance. That way your
"child"tables would become normal tables and you could use declarative partitioning on them.
 
>>>> Even if you are querying the TEMPLATE_TECH table, you could still do that by turning the TEMPLATE_TECH table into
aview which performs a UNION ALL over the other tables.
 
>>>
>>
>> -- 
>> Adrian Klaver
>> adrian.klaver@aklaver.com
> 
> 

-- 
Adrian Klaver
adrian.klaver@aklaver.com

Adrian Klaver <adrian.klaver@aklaver.com> escribió:

> On 11/1/24 13:47, Thiemo Kellner wrote:
>> It looks to me basically to be a "create table A as select * from B  
>> where false".
>
> No it more capable then that.

Yes, I wrote basically, not exactly.

> CREATE TABLE <some_tbl> LIKE <some_other_tbl> has  like_option which  
> allows to transfer over more attributes of the table, for example  
> defaults, constraints, indexes, etc.

But, to my understanding, no primary nor unique nor foreign constraint.

On 11/1/24 16:10, thiemo@gelassene-pferde.biz wrote:
> 
> Adrian Klaver <adrian.klaver@aklaver.com> escribió:
> 
>> On 11/1/24 13:47, Thiemo Kellner wrote:
>>> It looks to me basically to be a "create table A as select * from B 
>>> where false".
>>
>> No it more capable then that.
> 
> Yes, I wrote basically, not exactly.
> 
>> CREATE TABLE <some_tbl> LIKE <some_other_tbl> has  like_option which 
>> allows to transfer over more attributes of the table, for example 
>> defaults, constraints, indexes, etc.
> 
> But, to my understanding, no primary nor unique nor foreign constraint.
> 


"INCLUDING INDEXES

     Indexes, PRIMARY KEY, UNIQUE, and EXCLUDE constraints on the 
original table will be created on the new table. Names for the new 
indexes and constraints are chosen according to the default rules, 
regardless of how the originals were named. (This behavior avoids 
possible duplicate-name failures for the new indexes.)
"

FK's are not in the the INCLUDINGs, nor triggers.


-- 
Adrian Klaver
adrian.klaver@aklaver.com

My bad. I was expecting primary and unique to be mentioned here, so I did not read on.


**INCLUDING CONSTRAINTS***
**#[https://www.postgresql.org/docs/current/sql-createtable.html#SQL-CREATETABLE-PARMS-LIKE-OPT-CONSTRAINTS]*

/*CHECK*// constraints will be copied. No distinction is made between column constraints and table constraints.
Not-nullconstraints are always copied to the new table./ 


02.11.2024 00:53:53 Adrian Klaver <adrian.klaver@aklaver.com>:

> On 11/1/24 16:10, thiemo@gelassene-pferde.biz wrote:
>> Adrian Klaver <adrian.klaver@aklaver.com> escribió:
>> On 11/1/24 13:47, Thiemo Kellner wrote:
>>>> It looks to me basically to be a "create table A as select * from B where false".
>>>
>>> No it more capable then that.
>> Yes, I wrote basically, not exactly.
>> CREATE TABLE <some_tbl> LIKE <some_other_tbl> has  like_option which allows to transfer over more attributes of the
table,for example defaults, constraints, indexes, etc. 
>> But, to my understanding, no primary nor unique nor foreign constraint.
>>
>
>
> "INCLUDING INDEXES
>
>      Indexes, PRIMARY KEY, UNIQUE, and EXCLUDE constraints on the original table will be created on the new table.
Namesfor the new indexes and constraints are chosen according to the default rules, regardless of how the originals
werenamed. (This behavior avoids possible duplicate-name failures for the new indexes.) 
> "
>
> FK's are not in the the INCLUDINGs, nor triggers.
>
>
> --
> Adrian Klaver
> adrian.klaver@aklaver.com