spanner/spansql: Support conditional expressions

[tyamagu2]

spansql fails to parse statements that contain conditional expressions like SELECT CASE 1 WHEN 1 THEN "X" WHEN 2 THEN "Y" ELSE NULL END.

[rahul2393]

Hello @tyamagu2, thanks for opening the issue here, can you share your brief usecase for using spansql/spannertest, spansql/spannertest packages lag behind compared to the actualy cloud spanner feature wise and functionality wise, We are thinking of freezing the development of spansql/spannertest packages and recommend to use officially supported https://cloud.google.com/spanner/docs/emulator for in-memory usage.

[tyamagu2]

Hi @rahul2393 . I actually don't use spansql/spannertest. I use cloudspannerecosystem/yo to generate go code from spanner DDL file, and yo v2 uses spansql to parse DDL statements. I'm trying to generate code from the DDL statement that contains a column definition like the following, so I need spansql to support parsing either CASE or IF expression.

InProgress BOOL AS (CASE WHEN Status = "in_progress" THEN TRUE ELSE NULL END) STORED

[rahul2393]

ok in the Readme of cloudspannerecosystem/yo its mentioned that application is not officially supported as part of the Cloud Spanner product but since the change is small it's ok for now.