Documentation, firebird.conf

builds/install/misc/firebird.conf.in

@@ -429,8 +429,8 @@
 # plugin using SHA-1 for the client proof. This enables backwards compatibility
 # with old Firebird 3 servers but does not comply with NIST security requirements.
 #
-# The default client configuration (AuthClient) also supports the pre-Firebird 3 legacy 
+# The default client configuration (AuthClient) also supports the pre-Firebird 3 legacy
-# authentication protocol (Legacy_Auth). This is again for backwards 
+# authentication protocol (Legacy_Auth). This is again for backwards
 # compatibility but has many known weaknesses and is deprecated for current use.
 #
 # The default Windows client configuration (AuthClient) also includes support for
@@ -657,7 +657,7 @@
 # mode by default. In this mode rec_version/no_rec_version transaction flags have
 # no effect. Setting this parameter to 0 effectively reverts engine to legacy
 # behavior.
-# 
+#
 # CAUTION!
 # There is no guarantee that legacy behavior will be available in future Firebird
 # versions.
@@ -666,6 +666,20 @@
 #
 #ReadConsistency = 1
 
+# ----------------------------
+# Engine currently provides a number of new datatypes unknown to legacy clients.
+# In order to simplify use of old applications set this parameter to minor FB
+# version datatype compatibility with which you need. Currently two values are
+# supported: 3.0 & 2.5.
+# More precise (including per-session) tuning is possible via SQL and DPB.
+#
+# Per-database configurable.
+#
+#	Type: string
+#
+#DataTypeCompatibility =
+
+
 # ----------------------------
 # Client Connection Settings (Basic)
 #

doc/sql.extensions/README.set_bind.md

@@ -20,23 +20,45 @@ SET BIND OF type NATIVE;
 Makes it possible to define rules of describing types of returned to the client columns in non-standard way -
 `type-from` is replaced with `type-to`, automatic data coercion takes place.
 
-Except SQL-statement there are two more ways to specify data coercion - tag `isc_dpb_bind` in DPB
-and `SetBind` parameter in firebird.conf & databases.conf. The later the rule is introduced (.conf->DPB->SQL)
-the higher priotiy it has. I.e. one can override any preconfigured settings from SQL statement.
-
 When incomplete type definition is used (i.e. `CHAR` instead `CHAR(n)`) in left part of `SET BIND` coercion
 will take place for all `CHAR` columns, not only default `CHAR(1)`.
 When incomplete type definiton is used in right side of the statement (TO part) firebird engine will define missing
 details about that type automatically based on source column.
 
 Special `TO` part format `LEGACY` is used when datatype, missing in previous FB version, should be represented in
-a way, understandable by old client software (may be with some data losses). For example, `NUMERIC(38)` in legacy
+a way, understandable by old client software (may be with some data losses). The following coercions are done for
-form will be represented as `NUMERIC(18)`.
+legacy datatypes:
+
+| Native datatype | Legacy datatype |
+|---|---|
+| BOOLEAN | CHAR(5) |
+| DECFLOAT | DOUBLE PRECISION |
+| NUMERIC(38) | NUMERIC(18) |
+| TIME WITH TIME ZONE | TIME WITHOUT TIME ZONE |
+| TIMESTAMP WITH TIME ZONE | TIMESTAMP WITHOUT TIME ZONE |
 
 Setting `NATIVE` means `type` will be used as if there were no previous rules for it.
 
+Except SQL-statement there are two more ways to specify data coercion - tag `isc_dpb_bind` in DPB
+and `DataTypeCompatibility` parameter in firebird.conf & databases.conf. The later the rule is introduced
+(.conf->DPB->SQL) the higher priotiy it has.
+I.e. one can override .conf in any other way any DPB from SQL statement.
 
-### Samples:
+Value of clumplet with `isc_dpb_bind` tag in DPB should be specified as a set of partially
+formed SET BIND statements, i.e. with prefix SET BIND OF is omitted, separated by semicolons.
+For example:
+```c++
+dpb->insertString(&status, isc_dpb_bind, "decfloat to char; numeric(38) to char");
+```
+
+`DataTypeCompatibility` is minor firebird version for which we want to provide some compatibility
+regarding data types. That compatibility may be not absolute - for example SET BIND can't care about type
+of particular SQL functions. The following types will be described in legacy form when `DataTypeCompatibility=3.0:`
+DECFLOAT, NUMERIC(38) and TIME(STAMP) WITH TIME ZONE. When `DataTypeCompatibility=2.5` in addition to this
+list BOOLEAN will be described as legacy type as well.
+
+
+### SQL Samples:
 
 ```sql
 SELECT CAST('123.45' AS DECFLOAT(16)) FROM RDB$DATABASE;	--native