Re: [sqlalchemy] Representing Tree Structures with sqlAlchemy

[Nathan Mooth]

Thanks for the example, it was exactly what I was looking for.

On Friday, July 21, 2017 at 10:47:16 AM UTC-6, Mike Bayer wrote:
>
> On Fri, Jul 21, 2017 at 11:40 AM, Nathan Mooth  > wrote: 
> > So I have a tree-like data structure that I need to store in a way so 
> that I 
> > can see all children or all parents of a query as well as their relative 
> > depth from the query item. In the past I have been using the closure 
> table 
> > method demonstrated in this blog post, however now that I am switching 
> to 
> > sqlAlchemy I am wondering if there is a better way to do this. So 
> basically 
> > I am trying to figure out how to run a series of inserts on my closure 
> table 
> > whenever an item is added to the main table, as well as what would be 
> the 
> > best way to load the child or parent items of a query. 
>
> you'd likely want to use the same approaches illustrated in the nested 
> sets example at 
>
> http://docs.sqlalchemy.org/en/latest/_modules/examples/nested_sets/nested_sets.html
>  
> - basically intercept before_insert(), or after_insert(), the run the 
> additional SQL you need on the given connection within the flush 
> process.The query approach is also illustrated there. 
>
> If you're just going for in-memory, "load a node, then access 
> node.children", and you don't need elaborate cross-depth searching and 
> set operations, then all of these approaches are far too complicated, 
> just use adjacency list. 
>
>
>
>
>
> > 
> > -- 
> > SQLAlchemy - 
> > The Python SQL Toolkit and Object Relational Mapper 
> > 
> > http://www.sqlalchemy.org/ 
> > 
> > To post example code, please provide an MCVE: Minimal, Complete, and 
> > Verifiable Example. See http://stackoverflow.com/help/mcve for a full 
> > description. 
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>

-- 
SQLAlchemy - 
The Python SQL Toolkit and Object Relational Mapper

http://www.sqlalchemy.org/

To post example code, please provide an MCVE: Minimal, Complete, and Verifiable 
Example.  See  http://stackoverflow.com/help/mcve for a full description.
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Re: [sqlalchemy] Representing Tree Structures with sqlAlchemy

[Mike Bayer]

On Fri, Jul 21, 2017 at 11:40 AM, Nathan Mooth  wrote:
> So I have a tree-like data structure that I need to store in a way so that I
> can see all children or all parents of a query as well as their relative
> depth from the query item. In the past I have been using the closure table
> method demonstrated in this blog post, however now that I am switching to
> sqlAlchemy I am wondering if there is a better way to do this. So basically
> I am trying to figure out how to run a series of inserts on my closure table
> whenever an item is added to the main table, as well as what would be the
> best way to load the child or parent items of a query.

you'd likely want to use the same approaches illustrated in the nested
sets example at
http://docs.sqlalchemy.org/en/latest/_modules/examples/nested_sets/nested_sets.html
- basically intercept before_insert(), or after_insert(), the run the
additional SQL you need on the given connection within the flush
process.The query approach is also illustrated there.

If you're just going for in-memory, "load a node, then access
node.children", and you don't need elaborate cross-depth searching and
set operations, then all of these approaches are far too complicated,
just use adjacency list.





>
> --
> SQLAlchemy -
> The Python SQL Toolkit and Object Relational Mapper
>
> http://www.sqlalchemy.org/
>
> To post example code, please provide an MCVE: Minimal, Complete, and
> Verifiable Example. See http://stackoverflow.com/help/mcve for a full
> description.
> ---
> You received this message because you are subscribed to the Google Groups
> "sqlalchemy" group.
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> Visit this group at https://groups.google.com/group/sqlalchemy.
> For more options, visit https://groups.google.com/d/optout.

-- 
SQLAlchemy - 
The Python SQL Toolkit and Object Relational Mapper

http://www.sqlalchemy.org/

To post example code, please provide an MCVE: Minimal, Complete, and Verifiable 
Example.  See  http://stackoverflow.com/help/mcve for a full description.
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[sqlalchemy] Representing Tree Structures with sqlAlchemy

[Nathan Mooth]

So I have a tree-like data structure that I need to store in a way so that 
I can see all children or all parents of a query as well as their relative 
depth from the query item. In the past I have been using the closure table 
method demonstrated in this blog post 
, 
however now that I am switching to sqlAlchemy I am wondering if there is a 
better way to do this. So basically I am trying to figure out how to run a 
series of inserts on my closure table whenever an item is added to the main 
table, as well as what would be the best way to load the child or parent 
items of a query.

-- 
SQLAlchemy - 
The Python SQL Toolkit and Object Relational Mapper

http://www.sqlalchemy.org/

To post example code, please provide an MCVE: Minimal, Complete, and Verifiable 
Example.  See  http://stackoverflow.com/help/mcve for a full description.
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