Confusing semantic of IMPORT_FROM_EXA parameter

[exaSR]

• Observation:
  • IMPORT_FROM_EXA = 'false' does not work
  • ALTER VIRTUAL SCHEMA CDP3_CDP SET IMPORT_FROM_EXA = Null; works
• Expected: IMPORT_FROM_EXA = 'false' works, too

Original Report

Adapter Version: virtual-schema-dist-10.1.0-exasol-7.0.2

Given the example usage of

IMPORT_FROM_EXA = 'true'

One would assume that an explicit negation should work; alas, it does not:

CREATE VIRTUAL SCHEMA CDP3_CDP
USING VSA.EXASOL_ADAPTER WITH
    CONNECTION_NAME = 'CDP_JDBC'
    SCHEMA_NAME     = 'CDP'
    IMPORT_FROM_EXA = 'false'
;
-- takes a few seconds to read metadata

select count(*) from cdp3_cdp.account_sf;
-- results in error:

[Code: 0, SQL State: 22002]  VM error: F-UDF-CL-LIB-1126: F-UDF-CL-SL-JAVA-1006: F-UDF-CL-SL-JAVA-1026: 
com.exasol.ExaUDFException: F-UDF-CL-SL-JAVA-1068: Exception during singleCall adapterCall 
java.lang.IllegalArgumentException: E-VSEXA-1: Incomplete remote connection information Please specify a named EXA connection 'EXA_CONNECTION' for the ExaLoader and a named JDBC connection with 'CONNECTION_NAME' for the Virtual Schema adapter.
com.exasol.adapter.dialects.exasol.ExasolConnectionDefinitionBuilder.buildImportFromExaConnectionDefinition(ExasolConnectionDefinitionBuilder.java:40)
com.exasol.adapter.dialects.exasol.ExasolConnectionDefinitionBuilder.buildConnectionDefinition(ExasolConnectionDefinitionBuilder.java:23)
com.exasol.adapter.dialects.rewriting.AbstractQueryRewriter.rewrite(AbstractQueryRewriter.java:49)
com.exasol.adapter.dialects.AbstractSqlDialect.rewriteQuery(AbstractSqlDialect.java:141)
com.exasol.adapter.jdbc.JDBCAdapter.pushdown(JDBCAdapter.java:243)
com.exasol.adapter.AdapterCallExecutor.executePushDownRequest(AdapterCallExecutor.java:117)
com.exasol.adapter.request.PushDownRequest.executeWith(PushDownRequest.java:66)
com.exasol.adapter.AdapterCallExecutor.executeAdapterCall(AdapterCallExecutor.java:34)
com.exasol.adapter.RequestDispatcher.processAdapterCall(RequestDispatcher.java:55)
com.exasol.adapter.RequestDispatcher.adapterCall(RequestDispatcher.java:33)
com.exasol.ExaWrapper.runSingleCall(ExaWrapper.java:101)
 (Session: 1758344366162313216)

[exaSR]

Update:

ALTER VIRTUAL SCHEMA CDP3_CDP SET IMPORT_FROM_EXA = Null;

seems to work.

[ckunki]

Root cause seems to be that

• some places handle IMPORT_FROM_EXA as an adapter property expecting a string representing boolean value (i.e. "true" or "false", case-insensitive)
• other places just check if the adapter property is present (regardless of the value)

I propose to change implementation to the following behavior

• ✅ explicitly define IMPORT_FROM_EXA as an optional boolean adapter property
• ✅if property has a value other than "true" or "false", case-insensitive then VSEXA throws an exception
• ✅if property is specified with value "true" then import-semantics is used
• ⚠️ in all other cases import-semantics is not used

Icon ✅ signals functionality already implemented by VSEXA version 7.1.1 Icon ⚠️ signals changed planned in the scope of the current ticket

[exaSR]

Sounds great!

[ckunki]

Thanks for immediate feedback - sorry, for the issue waiting some weeks.