Subject Re: [IB-Architect] SQL Statement Depandance Mapping
Author Charlie Caro
Jim Starkey wrote:
> DDL is a different story. The real DDL operations are performed
> by ordinary DML to the system tables. SQL DDL is what is known
> in the biz as syntactic sugar.

The DSQL component emits BLR for DML statements and something
called DYN (dynamic DDL) for DDL statements. DYN is yet another
byte encoded language for describing data definition statements.

Jim created the DYN language when our VARs were demanding a way
to upgrade their customers databases in the field. The customers'
databases were licensed for run-time operation only. The high-level
tool, GDEF, which performed DDL operations was unlicensed. So, Jim
created a low-level, byte-encoded language which GDEF generated
from a high-level, GDEF script. The VARs could then distribute the
machine-generated DYN to their clients to modify the underlying
metadata. I guess you could call DYN an obfuscated, back door for
metadata operations.

Today, the same server-side DSQL parser generates parse trees for
both SQL DML and DDL statements. The DDL parse trees are passed
to a component which emits DYN. That DYN is immediately passed to
the Y-valve entrypoint ISC_DDL which interprets the DYN and performs
the actions on the system tables.

So the behavior is as Jim describes but the path is a bit more
circuitous than one would expect.