Data type conversion control

The fglcomp and fglform compilers expect known language data types (FGL types) in the schema file. While most data types correspond to IBM® Informix® SQL data types, some databases (including Informix) can use specific types that do not map to an FGL type. Therefore, data types in the schema file are generated from the system catalog tables based on some conversion rules.

Type conversion can be controlled with the -cv option. Each character position of the string passed by this option represents a line in the conversion table of the corresponding source database. Give a conversion code for each data type (for example: -cv AABAAAB).

When using X as conversion code, the columns using the corresponding data types will be ignored and not written to the .sch file. This is particularly useful in the case of auto-generated columns like SQL Server's uniqueidentifier data type, when using a DEFAULT NEWID() clause.

Run the tool with the -ct option to see all the data type conversion tables, or use the -cx dbtype option to display the conversion table for a given database type (dbtype must be ifx, ora, db2, msv, pgs, mys, ...).

fgldbsch -cx ifx
Informix        Informix A          Informix B
1 BOOLEAN       BOOLEAN (t=45)      CHAR(1)
2 INT8          INT8                DECIMAL(19,0)
3 SERIAL8       SERIAL8             DECIMAL(19,0)
4 LVARCHAR(m)   VARCHAR2(m)         VARCHAR2(m)
5 BIGINT        BIGINT              DECIMAL(19,0)
(ns) = Not supported in 4gl.
fgldbsch -db test1 -cv BAAABB

In the above example, the -cv option instructs fgldbsch to use the types of the "Informix A" column for all original column types except for BOOLEAN, BIGINT and BIGSERIAL, which must be converted to a VARCHAR2(m) FGL type.

The IBM Informix LVARCHAR(m) type can be converted by default to a VARCHAR2(m) pseudo type (code 201), which will be identified as a VARCHAR(m) by compilers.

In schema files, VARCHAR2(m) (type code 201) is equivalent to VARCHAR(m) (type code 13), without the 255 bytes limitation of the original Informix VARCHAR type.

Not all native data types can be converted to FGL types. For example, user-defined types or spatial types are not supported by the language. When a table column with such unsupported data type is found, fgldbsch stops and displays an error to bring the problem to your attention. Use the -ie option of fgldbsch to ignore the database tables having columns with unsupported types. When this option is used, none of the table columns definition will be written to the schema file.