SQL is the language you use to make requests of Vantage. That is, you use SQL to query Vantage.
The SQL parser handles incoming SQL requests in the following sequence:
- If the Parser finds the request in the Request cache, it does the following:
- Reuses the plastic steps in the cache and passes them to gncApply. (Plastic steps are directives to the database management system that do not contain data values.)
- Goes to step 4 and then to step 8.
- The Syntaxer checks the syntax of the request for errors.
If there are no errors, the Syntaxer converts the request to a parse tree and passes it to the Resolver.
If there are errors, the Syntaxer passes an error message back to the requestor and stops.
- The Resolver adds information from the Data Dictionary (or a cached copy of the information) to convert database, table, view, stored procedure, and macro names to internal identifiers.
- The security module checks privileges in the Data Dictionary.
If the privileges are valid, the Security module passes the request to the Optimizer.
If the privileges are invalid, the Security module aborts the request and passes an error message and stops.
- The Optimizer determines the most effective way to implement the SQL request.
- The Optimizer scans the request to determine where to put locks.
- The Optimizer passes the optimized parse tree to the Generator.
- The Generator transforms the optimized parse tree into plastic steps, caches the steps if appropriate, and passes them to gncApply.
- gncApply binds any parameterized data into the plastic steps and transforms the plastic steps into concrete steps.
Concrete steps are directives to the AMPs that contain any needed user- or session-specific values and any needed data parcels.
- gncApply passes the concrete steps to the Dispatcher.