#120: Supported using the push down request to specify the datatypes…

… of result set.

.gitattributes

@@ -0,0 +1,11 @@
+dependencies.md                                                  linguist-generated=true
+doc/changes/changelog.md                                         linguist-generated=true
+pk_generated_parent.pom                                          linguist-generated=true
+.github/workflows/broken_links_checker.yml                       linguist-generated=true
+.github/workflows/ci-build-next-java.yml                         linguist-generated=true
+.github/workflows/ci-build.yml                                   linguist-generated=true
+.github/workflows/dependencies_check.yml                         linguist-generated=true
+.github/workflows/release_droid_prepare_original_checksum.yml    linguist-generated=true
+.github/workflows/release_droid_print_quick_checksum.yml         linguist-generated=true
+.github/workflows/release_droid_release_on_maven_central.yml     linguist-generated=true
+.github/workflows/release_droid_upload_github_release_assets.yml linguist-generated=true

.gitignore

@@ -30,4 +30,6 @@ pom.xml.versionsBackup
 *.orig
 *.old
 *.md.html
-*.flattened-pom.xml
+*.flattened-pom.xml
+/.apt_generated/
+/.apt_generated_tests/

doc/changes/changes_10.0.0.md

@@ -0,0 +1,17 @@
+# Virtual Schema Common JDBC 10.0.0, released 2022-??-??
+
+Code name: Read Expected Datatypes From Request
+
+## Summary
+
+Starting with major version 8 Exasol database uses the capabilities reported by each virtual schema to provide select list data types for each push down request. Based on this information the JDBC virtual schemas no longer need to infer the data types of the result set by inspecting its values. Instead the JDBC virtual schemas can now use the information provided by the database.
+
+## Features
+
+* #120: Supported using the push down request to specify the datatypes of result set.
+
+## Dependency Updates
+
+### Compile Dependency Updates
+
+* Updated `com.exasol:virtual-schema-common-java:15.3.2` to `16.0.0`

pom.xml

@@ -1,10 +1,9 @@
 <?xml version="1.0" encoding="UTF-8" standalone="no"?>
-<project xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://maven.apache.org/POM/4.0.0"
-         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
     <modelVersion>4.0.0</modelVersion>
     <groupId>com.exasol</groupId>
     <artifactId>virtual-schema-common-jdbc</artifactId>
-    <version>9.0.5</version>
+    <version>10.0.0</version>
     <name>Virtual Schema Common JDBC</name>
     <description>Common module for JDBC-based data access from Virtual Schemas.</description>
     <url>https://github.com/exasol/virtual-schema-common-jdbc/</url>
@@ -28,7 +27,7 @@
         <dependency>
             <groupId>com.exasol</groupId>
             <artifactId>virtual-schema-common-java</artifactId>
-            <version>15.3.2</version>
+            <version>16.0.0</version>
         </dependency>
         <dependency>
             <groupId>javax.xml.bind</groupId>
@@ -144,7 +143,7 @@
     <parent>
         <artifactId>virtual-schema-common-jdbc-generated-parent</artifactId>
         <groupId>com.exasol</groupId>
-        <version>9.0.5</version>
+        <version>10.0.0</version>
         <relativePath>pk_generated_parent.pom</relativePath>
     </parent>
 </project>

src/main/java/com/exasol/adapter/dialects/AbstractSqlDialect.java

@@ -16,6 +16,7 @@
 import com.exasol.adapter.dialects.rewriting.SqlGenerationVisitor;
 import com.exasol.adapter.jdbc.ConnectionFactory;
 import com.exasol.adapter.jdbc.RemoteMetadataReader;
+import com.exasol.adapter.metadata.DataType;
 import com.exasol.adapter.metadata.SchemaMetadata;
 import com.exasol.adapter.sql.*;
 import com.exasol.errorreporting.ExaError;
@@ -134,9 +135,9 @@ public Map<ScalarFunction, String> getPrefixFunctionAliases() {
     }
 
     @Override
-    public String rewriteQuery(final SqlStatement statement, final ExaMetadata exaMetadata)
-            throws AdapterException, SQLException {
-        return createQueryRewriter().rewrite(statement, exaMetadata, this.properties);
+    public String rewriteQuery(final SqlStatement statement, final List<DataType> selectListDataTypes,
+            final ExaMetadata exaMetadata) throws AdapterException, SQLException {
+        return createQueryRewriter().rewrite(statement, selectListDataTypes, exaMetadata, this.properties);
     }
 
     @Override
@@ -151,7 +152,7 @@ public SchemaMetadata readSchemaMetadata(final List<String> tables) {
 
     /**
      * Quote a string literal with single quotes.
-     * 
+     *
      * @param value string literal
      * @return quoted string
      */
@@ -165,7 +166,7 @@ public String quoteLiteralStringWithSingleQuote(final String value) {
 
     /**
      * Quote an identifier with double quotes.
-     * 
+     *
      * @param identifier identifier to quote
      * @return quoted identifier
      */
@@ -185,7 +186,7 @@ public void validateProperties() throws PropertyValidationException {
 
     /**
      * Validate that all given properties are supported by the dialect.
-     * 
+     *
      * @throws PropertyValidationException if validation fails
      */
     protected void validateSupportedPropertiesList() throws PropertyValidationException {
@@ -199,7 +200,7 @@ protected void validateSupportedPropertiesList() throws PropertyValidationExcept
 
     /**
      * Create an exception for an unsupported property.
-     * 
+     *
      * @param unsupportedElement unsupported property name.
      * @param property           unsupported property name
      * @return exception
@@ -236,7 +237,7 @@ private void validateSchemaNameProperty() throws PropertyValidationException {
 
     /**
      * Validate the input of a boolean property.
-     * 
+     *
      * @param property property name
      * @throws PropertyValidationException if validation fails
      */
@@ -339,7 +340,7 @@ protected void checkImportPropertyConsistency(final String importFromProperty, f
 
     /**
      * Validate the value of the castNumberToDecimalProperty.
-     * 
+     *
      * @param castNumberToDecimalProperty property name
      * @throws PropertyValidationException if validation fails
      */

src/main/java/com/exasol/adapter/dialects/QueryRewriter.java

@@ -1,10 +1,12 @@
 package com.exasol.adapter.dialects;
 
 import java.sql.SQLException;
+import java.util.List;
 
 import com.exasol.ExaMetadata;
 import com.exasol.adapter.AdapterException;
 import com.exasol.adapter.AdapterProperties;
+import com.exasol.adapter.metadata.DataType;
 import com.exasol.adapter.sql.SqlStatement;
 
 /**
@@ -28,13 +30,14 @@ public interface QueryRewriter {
     /**
      * Set the original push-down statement.
      *
-     * @param statement   SQL statement that represents the original push-down query
-     * @param properties  user-defined adapter properties
-     * @param exaMetadata Exasol metadata
+     * @param statement           SQL statement that represents the original push-down query
+     * @param selectListDataTypes expected data types of result set
+     * @param properties          user-defined adapter properties
+     * @param exaMetadata         Exasol metadata
      * @return rewritten query
      * @throws AdapterException if rewriting fails
      * @throws SQLException     if any SQL commands executed on the remote data source failed during rewriting
      */
-    public String rewrite(final SqlStatement statement, final ExaMetadata exaMetadata,
-            final AdapterProperties properties) throws AdapterException, SQLException;
+    public String rewrite(final SqlStatement statement, List<DataType> selectListDataTypes,
+            final ExaMetadata exaMetadata, final AdapterProperties properties) throws AdapterException, SQLException;
 }

src/main/java/com/exasol/adapter/dialects/SqlDialect.java

@@ -8,6 +8,7 @@
 import com.exasol.adapter.AdapterException;
 import com.exasol.adapter.capabilities.Capabilities;
 import com.exasol.adapter.dialects.rewriting.SqlGenerationContext;
+import com.exasol.adapter.metadata.DataType;
 import com.exasol.adapter.metadata.SchemaMetadata;
 import com.exasol.adapter.sql.*;
 
@@ -239,11 +240,13 @@ public enum NullSorting {
      * Rewrite the given query so that data from the remote data source is imported into Exasol when that query is
      * executed on the Virtual Schema frontend.
      *
-     * @param statement   original query as sent by the Virtual Schema frontend
-     * @param exaMetadata Exasol metadata
+     * @param statement           original query as sent by the Virtual Schema frontend
+     * @param selectListDataTypes expected datatypes of the result set
+     * @param exaMetadata         Exasol metadata
      * @return rewritten query
      * @throws SQLException     if execution of any SQL command on the remote data source failed
      * @throws AdapterException if rewriting the query failed
      */
-    public String rewriteQuery(SqlStatement statement, ExaMetadata exaMetadata) throws AdapterException, SQLException;
+    public String rewriteQuery(SqlStatement statement, List<DataType> selectListDataTypes, ExaMetadata exaMetadata)
+            throws AdapterException, SQLException;
 }

src/main/java/com/exasol/adapter/dialects/rewriting/AbstractQueryRewriter.java

@@ -1,6 +1,7 @@
 package com.exasol.adapter.dialects.rewriting;
 
 import java.sql.SQLException;
+import java.util.List;
 import java.util.logging.Logger;
 
 import com.exasol.*;
@@ -9,6 +10,7 @@
 import com.exasol.adapter.dialects.*;
 import com.exasol.adapter.jdbc.ConnectionDefinitionBuilder;
 import com.exasol.adapter.jdbc.RemoteMetadataReader;
+import com.exasol.adapter.metadata.DataType;
 import com.exasol.adapter.sql.SqlStatement;
 import com.exasol.errorreporting.ExaError;
 
@@ -39,13 +41,14 @@ protected AbstractQueryRewriter(final SqlDialect dialect, final RemoteMetadataRe
     }
 
     @Override
-    public String rewrite(final SqlStatement statement, final ExaMetadata exaMetadata,
-            final AdapterProperties properties) throws AdapterException, SQLException {
+    public String rewrite(final SqlStatement statement, final List<DataType> selectListDataTypes,
+            final ExaMetadata exaMetadata, final AdapterProperties properties) throws AdapterException, SQLException {
         final String pushdownQuery = createPushdownQuery(statement, properties);
         final ExaConnectionInformation exaConnectionInformation = getConnectionInformation(exaMetadata, properties);
         final String connectionDefinition = this.connectionDefinitionBuilder.buildConnectionDefinition(properties,
                 exaConnectionInformation);
-        final String importStatement = generateImportStatement(connectionDefinition, pushdownQuery);
+        final String importStatement = generateImportStatement(connectionDefinition, selectListDataTypes,
+                pushdownQuery);
         LOGGER.finer(() -> "Import push-down statement:\n" + importStatement);
         return importStatement;
     }
@@ -63,7 +66,7 @@ private String createPushdownQuery(final SqlStatement statement, final AdapterPr
 
     /**
      * Read the connection information from the metadata.
-     * 
+     *
      * @param exaMetadata metadata
      * @param properties  adapter properties
      * @return connection information
@@ -90,10 +93,11 @@ protected ExaConnectionInformation getConnectionInformation(final ExaMetadata ex
      * executed in the external source be as source data.
      *
      * @param connectionDefinition connection definition to be used when connecting to the external source
+     * @param selectListDataTypes  TODO
      * @param pushdownQuery        source data for the `IMPORT...FROM` statement
      * @return IMPORT statement to be executed on the Exasol database
      * @throws SQLException if any problem occurs
      */
-    protected abstract String generateImportStatement(final String connectionDefinition, final String pushdownQuery)
-            throws SQLException;
+    protected abstract String generateImportStatement(final String connectionDefinition,
+            List<DataType> selectListDataTypes, final String pushdownQuery) throws SQLException;
 }

src/main/java/com/exasol/adapter/dialects/rewriting/ImportFromJDBCQueryRewriter.java

@@ -1,9 +1,11 @@
 package com.exasol.adapter.dialects.rewriting;
 
 import java.sql.SQLException;
+import java.util.List;
 
 import com.exasol.adapter.dialects.SqlDialect;
 import com.exasol.adapter.jdbc.*;
+import com.exasol.adapter.metadata.DataType;
 
 /**
  * Implementation of {@link AbstractQueryRewriter} to generate {@code IMPORT FROM JDBC} queries.
@@ -34,7 +36,7 @@ public ImportFromJDBCQueryRewriter(final SqlDialect dialect, final RemoteMetadat
     }
 
     @Override
-    protected String generateImportStatement(final String connectionDefinition, final String pushdownQuery)
+    protected String generateImportStatement(final String connectionDefinition, List<DataType> selectListDataTypes, final String pushdownQuery)
             throws SQLException {
         return "IMPORT FROM JDBC " + connectionDefinition + " STATEMENT '" + pushdownQuery.replace("'", "''") + "'";
     }

src/main/java/com/exasol/adapter/dialects/rewriting/ImportIntoTemporaryTableQueryRewriter.java

@@ -1,15 +1,17 @@
 package com.exasol.adapter.dialects.rewriting;
 
 import java.sql.SQLException;
+import java.util.List;
 import java.util.logging.Logger;
 
 import com.exasol.adapter.dialects.SqlDialect;
 import com.exasol.adapter.jdbc.*;
+import com.exasol.adapter.metadata.DataType;
 
 /**
  * Implementation of {@link AbstractQueryRewriter} to generate {@code IMPORT INTO (<columns description>) FROM JDBC}
  * queries.
- * 
+ *
  * @see <a href="https://docs.exasol.com/sql/import.htm">https://docs.exasol.com/sql/import.htm</a>
  */
 public class ImportIntoTemporaryTableQueryRewriter extends AbstractQueryRewriter {
@@ -44,20 +46,42 @@ public ImportIntoTemporaryTableQueryRewriter(final SqlDialect dialect,
         this.connectionFactory = connectionFactory;
     }
 
+    /*
+     * If selectListDataTypes is provided then use columns description from there otherwise infer columns description
+     * from query.
+     */
     @Override
-    protected String generateImportStatement(final String connectionDefinition, final String pushdownQuery)
-            throws SQLException {
-        final String columnDescription = this.createImportColumnsDescription(pushdownQuery);
-        return "IMPORT INTO (" + columnDescription + ") FROM JDBC " + connectionDefinition + " STATEMENT '"
+    protected String generateImportStatement(final String connectionDefinition,
+            final List<DataType> selectListDataTypes, final String pushdownQuery) throws SQLException {
+        final String columnsDescription = (selectListDataTypes.isEmpty() //
+                ? createColumnsDescriptionFromQuery(pushdownQuery)
+                : createColumnsDescriptionFromExpectedResult(selectListDataTypes));
+        return "IMPORT INTO (" + columnsDescription + ") FROM JDBC " + connectionDefinition + " STATEMENT '"
                 + pushdownQuery.replace("'", "''") + "'";
     }
 
-    private String createImportColumnsDescription(final String query) throws SQLException {
+    private String createColumnsDescriptionFromQuery(final String query) throws SQLException {
         final ColumnMetadataReader columnMetadataReader = this.remoteMetadataReader.getColumnMetadataReader();
         final ResultSetMetadataReader resultSetMetadataReader = new ResultSetMetadataReader(
                 this.connectionFactory.getConnection(), columnMetadataReader);
         final String columnsDescription = resultSetMetadataReader.describeColumns(query);
         LOGGER.finer(() -> "Import columns: " + columnsDescription);
         return columnsDescription;
     }
+
+    private String createColumnsDescriptionFromExpectedResult(final List<DataType> types) {
+        final StringBuilder builder = new StringBuilder();
+        int columnNumber = 1;
+        for (final DataType type : types) {
+            if (columnNumber > 1) {
+                builder.append(", ");
+            }
+            builder.append("c");
+            builder.append(columnNumber);
+            builder.append(" ");
+            builder.append(type.toString());
+            ++columnNumber;
+        }
+        return builder.toString();
+    }
 }