NUMERIC data types

Informix®

Informix supports several data types to store numbers:

Table 1. Informix numeric data types
Informix data type	Description
`SMALLINT`	16 bit signed integer
`INTEGER`	32 bit signed integer
`BIGINT`	64 bit signed integer
`INT8`	64 bit signed integer (replaced by `BIGINT`)
`DECIMAL`	Equivalent to `DECIMAL(16)`
`DECIMAL(p)`	Floating-point decimal number (max precision is 32)
`DECIMAL(p,s)`	Fixed-point decimal number (max precision is 32)
`MONEY`	Equivalent to `DECIMAL(16,2)`
`MONEY(p)`	Equivalent to `DECIMAL(p,2)` (max precision is 32)
`MONEY(p,s)`	Equivalent to `DECIMAL(p,s)` (max precision is 32)
`REAL / SMALLFLOAT`	32-bit floating point decimal (C float)
`DOUBLE PRECISION / FLOAT[(n)]`	64-bit floating point decimal (C double)

PostgreSQL

PostgreSQL supports the following data types to store numbers:

Table 2. PostgreSQL numeric data types
PostgreSQL data type	Description
`INT2 / SMALLINT`	16 bit signed integer
`INT4 / INTEGER`	32 bit signed integer
`INT8 / BIGINT`	64 bit signed integer
`DECIMAL(p,s)`	Decimals with precision and scale (fractional part)
`DECIMAL(p)`	Integers with p digits (no fractional part)
`DECIMAL`	Floating point numbers (no limit)
`FLOAT4`	16 bit variable precision
`FLOAT8`	32 bit variable precision

ANSI types like SMALLINT, INTEGER, FLOAT are supported by PostgreSQL as aliases to INT2, INT4 and FLOAT8 native types.

Informix DECIMAL(p) floating point types are converted to DECIMAL without precision/scale, to store any floating point number in PostgreSQL.

Solution

Use the following conversion rules to map Informix numeric types to PostgreSQL numeric types:

Table 3. Informix numeric data types and PostgreSQL equivalents
Informix data type	PostgreSQL equivalent
`SMALLINT`	`INT2`
`INTEGER`	`INT4`
`INT8 / BIGINT`	`INT8`
`DECIMAL(p,s)`	`DECIMAL(p,s)`
`DECIMAL(p)`	`DECIMAL`
`DECIMAL`	`DECIMAL`
`MONEY(p,s)`	`DECIMAL(p,s)`
`MONEY(p)`	`DECIMAL(p,2)`
`MONEY`	`DECIMAL(16,2)`
`SMALLFLOAT`	`FLOAT4`
`FLOAT[(n)]`	`FLOAT8`

The numeric types translation can be controlled with the following FGLPROFILE entries:

dbi.database.dsname.ifxemul.datatype.smallint = { true | false }
dbi.database.dsname.ifxemul.datatype.integer = { true | false }
dbi.database.dsname.ifxemul.datatype.bigint = { true | false }
dbi.database.dsname.ifxemul.datatype.int8 = { true | false }
dbi.database.dsname.ifxemul.datatype.decimal = { true | false }
dbi.database.dsname.ifxemul.datatype.money = { true | false }
dbi.database.dsname.ifxemul.datatype.float = { true | false }
dbi.database.dsname.ifxemul.datatype.smallfloat = { true | false }

For more details see IBM Informix emulation parameters in FGLPROFILE.