I assume that by GitHub page you mean [1]. For quite some time linq4j is part of calcite [2] so I think that [1] is not maintained anymore. The backlog in [1] also looks a bit obsolete. Julian can correct me if I am wrong.
In my previous email, I was talking about relational expressions (i.e., RelNode [3]) and not Expression [4] and Statement [5]. Furthermore, when I mentioned translating expressions to SQL what I had in mind is RelToSqlConverter [6]. Apologies for the confusion. I believe LINQ was introduced to bring procedural code and SQL closer and not use the one to replace the other. Best, Stamatis [1] https://github.com/julianhyde/linq4j [2] https://github.com/apache/calcite/tree/master/linq4j [3] https://github.com/apache/calcite/blob/master/core/src/main/java/org/apache/calcite/rel/RelNode.java [4] https://github.com/apache/calcite/blob/master/linq4j/src/main/java/org/apache/calcite/linq4j/tree/Expression.java [5] https://github.com/apache/calcite/blob/master/linq4j/src/main/java/org/apache/calcite/linq4j/tree/Statement.java [6] https://github.com/apache/calcite/blob/master/core/src/main/java/org/apache/calcite/rel/rel2sql/RelToSqlConverter.java On Wed, Apr 22, 2020 at 8:54 AM Ravi Kapoor <kapoorrav...@gmail.com> wrote: > Yeah Stamatis, I know that as I can see the github page for linq4j that > lots of task is in Backlog and Link-To-SQL Provider is one of them > But the intention of the project is to make java objects as Queryable talk > to DB. > > Expressions and various Statement used in linq4j is to generate the > different constructs like where filter, join to talk the back-end systems > as Sql Queries. > > But what about the normal While loop and If then else statements which is > not used in the Query-able objects . > Example could be below: > > > LOOP > SET heads = RAND() < 0.5; > IF heads THEN > SELECT 'Heads!'; > SET heads_count = heads_count + 1; > ELSE > SELECT 'Tails!'; > BREAK; > END IF; > END LOOP; > SELECT CONCAT(CAST(heads_count AS STRING), ' heads in a row'); > > > How linq4j going to convert normal while and If then else java expressions > to sql query if they are not involved in computation of sql constructs like > in lambda expression of filter. > > In one of the task in backlog I could see: > *In the prototype LINQ-to-SQL provider, write a simple rule to recognize a > select list and where clause and push them down to SQL.* > > I believe it was never intended for procedural code right? > > Thanks, > Ravi > > > On Wed, Apr 22, 2020 at 2:43 AM Stamatis Zampetakis <zabe...@gmail.com> > wrote: > > > Hi Ravi, > > > > As Julian already mentioned, we are quite far from what you would like to > > achieve. > > > > Nevertheless, I would like to mention that you can model certain kind of > > loops and recursion using the RepeatUnion [1] and Spool [2] relational > > expressions. Note that these APIs are experimental. > > > > Moreover, if your end goal is to push the computation in a DBMS, I have > to > > warn you that the code to translate these expressions back to SQL is not > > there yet. > > > > Best, > > Stamatis > > > > [1] > > > > > https://github.com/apache/calcite/blob/master/core/src/main/java/org/apache/calcite/rel/core/RepeatUnion.java > > [2] > > > > > https://github.com/apache/calcite/blob/master/core/src/main/java/org/apache/calcite/rel/core/Spool.java > > > > On Mon, Apr 20, 2020 at 8:08 PM Julian Hyde <jh...@apache.org> wrote: > > > > > Calcite relational expressions can represent SELECT, INSERT etc. but > not > > > procedural code. It’s a direction we could consider going. > > > > > > RexProgram is the closest thing we currently have to procedural code in > > > the algebra - single assignment of variables, use of variables in > > > expressions assigning to other variables - but it is a long way short > > > because there are no loops. > > > > > > > On Apr 19, 2020, at 12:47 PM, Ravi Kapoor <kapoorrav...@gmail.com> > > > wrote: > > > > > > > > Hi Team, > > > > > > > > I have my use where I need to convert my dialect specific stored > > > procedure > > > > constructs like while loop, If then else to Rel expression > > > > > > > > Basically this can contain control flow statements like below > > > > > > > > DECLARE heads BOOL; > > > > DECLARE heads_count INT64 DEFAULT 0; > > > > LOOP > > > > SET heads = RAND() < 0.5; > > > > IF heads THEN > > > > SELECT 'Heads!'; > > > > SET heads_count = heads_count + 1; > > > > ELSE > > > > SELECT 'Tails!'; > > > > BREAK; > > > > END IF; > > > > END LOOP; > > > > SELECT CONCAT(CAST(heads_count AS STRING), ' heads in a row'); > > > > > > > > > > > > I can create a Java AST model from the linq4j provided by calcite > > however > > > > this is only going to generate Java Result and I believe its only > used > > by > > > > the calcite for relational expressions of enumerable calling > convention > > > > which is used by adapters which does not support core relational > > > operations > > > > right? > > > > > > > > Is there a way I can convert the stored proc constructs into some > > > canonical > > > > form like Rel Tree and back to Stored proc of target dialect. > > > > -- > > > > > > > > Thanks, > > > > Ravi > > > > > > > > > > > -- > Thanks, > Ravi Kapoor > +91-9818764564 > kapoorrav...@gmail.com >
