Copy avoidance via static analysis for DBMS querying

1. A method comprising:

configuring, in a polyglot database management system (DBMS) that contains a guest language runtime environment, a database buffer that the guest language runtime environment does not manage;

invoking, in the polyglot DBMS, logic that is defined in a guest language to retrieve, into the database buffer that the guest language runtime environment does not manage, a value stored in a database in the polyglot DBMS;

analyzing, after said invoking the logic, the logic to detect that usage of the retrieved value cannot occur after the retrieved value is overwritten in the database buffer that the guest language runtime environment does not manage; and

executing, in response to detecting that usage of the retrieved value cannot occur after the retrieved value is overwritten in the database buffer, the logic without, after the retrieved value is overwritten in the database buffer, retaining a retained copy of the retrieved value in a memory region that the guest language runtime environment manages.

2. The method of claim 1 wherein said detecting that usage of the retrieved value cannot occur after the retrieved value is overwritten in the database buffer comprises detecting that the retrieved value cannot escape the logic that is defined in the guest language.

3. The method of claim 2 wherein:

the method further comprises after said invoking in the polyglot DBMS and before said detecting that usage of the retrieved value cannot occur after the retrieved value is overwritten in the database buffer, inlining a second logic into the logic that is defined in the guest language;

said detecting that the retrieved value cannot escape comprises detecting that the retrieved value cannot escape the second logic inlined into the logic that is defined in the guest language.

4. The method of claim 2 wherein said detecting that the retrieved value cannot escape comprises detecting that the retrieved value cannot escape a compilation unit that contains the logic that is defined in the guest language.

5. The method of claim 1 wherein said analyzing the logic comprises analyzing liveness of the retrieved value in the logic that is defined in the guest language.

6. The method of claim 5 wherein said analyzing liveness comprises exhaustively analyzing reachability, within the logic that is defined in the guest language, of the retrieved value.

7. The method of claim 5 wherein:

the logic that is defined in the guest language comprises a database invocation;

said analyzing liveness comprises graph coloring based on liveness of the retrieved value at the database invocation.

8. The method of claim 1 wherein:

the logic that is defined in the guest language defines a subroutine that accepts a parameter;

the database buffer contains a value of the parameter;

the method further comprises analyzing the logic to detect that usage of the value of the parameter cannot occur after the retrieved value is overwritten in the database buffer that the guest language runtime environment does not manage.

9. The method of claim 1 further comprising treating the retrieved value as causing, at a deoptimization point in the logic that is defined in the guest language, at least one selected from the group consisting of a liveness violation and escape of the retrieved value.

10. The method of claim 9 wherein the deoptimization point is based on a datatype of a column in said database in the polyglot DBMS.

11. The method of claim 1 further comprising performing at least one activity selected from the group consisting of:

storage, into the memory region that the guest language runtime environment manages, a proxy that intercepts said usage of the retrieved value, and

usage of a large object (LOB) in the database buffer to provide the retrieved value to the logic that is defined in the guest language.

12. The method of claim 1 wherein:

said defined to retrieve said value into the database buffer comprises configured to use a database object to retrieve said value into the database buffer;

the method further comprises detecting that said database object cannot escape the logic that is defined in the guest language.

13. The method of claim 12 wherein said detecting that said database object cannot escape comprises detecting that the logic that is defined in the guest language is not configured to initialize the database object.

14. The method of claim 1 wherein said analyzing the logic comprises performing at least one activity selected from the group consisting of:

compilation of a compilation unit that consists essentially of an entire subroutine or less than an entire subroutine,

compilation of a compilation unit that contains the logic that is defined in the guest language, and

analysis of an intermediate representation of the logic that can be executed by interpretation.

15. One or more non-transitory computer-readable media storing instructions that, when executed by one or more processors, cause:

configuring, in a polyglot database management system (DBMS) that contains a guest language runtime environment, a database buffer that the guest language runtime environment does not manage;

invoking, in the polyglot DBMS, logic that is defined in a guest language to retrieve, into the database buffer that the guest language runtime environment does not manage, a value stored in a database in the polyglot DBMS;

analyzing, after said invoking the logic, the logic to detect that usage of the retrieved value cannot occur after the retrieved value is overwritten in the database buffer that the guest language runtime environment does not manage; and

executing, in response to detecting that usage of the retrieved value cannot occur after the retrieved value is overwritten in the database buffer, the logic without, after the retrieved value is overwritten in the database buffer, retaining a retained copy of the retrieved value in a memory region that the guest language runtime environment manages.

16. The one or more non-transitory computer-readable media of claim 15 wherein said detecting that usage of the retrieved value cannot occur after the retrieved value is overwritten in the database buffer comprises detecting that the retrieved value cannot escape the logic that is defined in the guest language.

17. The one or more non-transitory computer-readable media of claim 15 wherein said analyzing the logic comprises analyzing liveness of the retrieved value in the logic that is defined in the guest language.

18. The one or more non-transitory computer-readable media of claim 15 wherein the instructions further cause treating the retrieved value as causing, at a deoptimization point in the logic that is defined in the guest language, at least one selected from the group consisting of a liveness violation and escape of the retrieved value.

19. The one or more non-transitory computer-readable media of claim 15 wherein the instructions further cause performing at least one activity selected from the group consisting of:

storage, into the memory region that the guest language runtime environment manages, a proxy that intercepts said usage of the retrieved value, and

usage of a large object (LOB) in the database buffer to provide the retrieved value to the logic that is defined in the guest language.

20. The one or more non-transitory computer-readable media of claim 15 wherein:

said defined to retrieve said value into the database buffer comprises configured to use a database object to retrieve said value into the database buffer;

the instructions further cause detecting that said database object cannot escape the logic that is defined in the guest language.