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* #75: Restricted amount of mapped tables in the remote schema to 100…
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…0. (#76)

* #75: Restricted amount of mapped tables in a remote schema to 1000.

Co-authored-by: Sebastian Bär <sebastian.baer@exasol.com>
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@AnastasiiaSergienko @redcatbear
AnastasiiaSergienko and redcatbear authored Dec 17, 2020
1 parent 474179d commit 9682fcb
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3 changes: 2 additions & 1 deletion doc/changes/changes_9.0.0.md
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Expand Up @@ -4,4 +4,5 @@ Code name:

## Refactoring

* #64: Refactored the `AbstractRemoteMetadataReader` and `TableMetadataReader` interface
* #64: Refactored the `AbstractRemoteMetadataReader` and `TableMetadataReader` interface
* #75: Restricted amount of mapped tables in the remote schema to 1000.
152 changes: 85 additions & 67 deletions src/main/java/com/exasol/adapter/jdbc/BaseTableMetadataReader.java
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Expand Up @@ -19,6 +19,7 @@ public class BaseTableMetadataReader extends AbstractMetadataReader implements T
static final String DEFAULT_TABLE_ADAPTER_NOTES = "";
private static final Logger LOGGER = Logger.getLogger(BaseTableMetadataReader.class.getName());
private static final Pattern UNQUOTED_IDENTIFIER_PATTERN = Pattern.compile("^[a-z][0-9a-z_]*");
private static final int DEFAULT_MAX_MAPPED_TABLE_LIST_SIZE = 1000;
protected ColumnMetadataReader columnMetadataReader;
private final IdentifierConverter identifierConverter;

Expand All @@ -40,118 +41,135 @@ public BaseTableMetadataReader(final Connection connection, final ColumnMetadata
@Override
public List<TableMetadata> mapTables(final ResultSet remoteTables, final List<String> selectedTables)
throws SQLException {
final List<TableMetadata> translatedTables = new ArrayList<>();
if (remoteTables.next()) {
do {
mapOrSkipTable(remoteTables, translatedTables, selectedTables);
} while (remoteTables.next());
return extractTableMetadata(remoteTables, selectedTables);
} else {
LOGGER.warning(() -> "Table scan did not find any tables. This can mean that either" //
+ " a) the source does not contain tables (yet)," + " b) the table type is not supported" //
+ " c) the table scan filter criteria is incorrect or" //
+ " d) the user does not have access permissions." //
+ " Please check that the source actually contains tables. " //
+ " Also check the spelling and exact case of any catalog or schema name you provided.");
return Collections.emptyList();
}
return translatedTables;
}

protected void mapOrSkipTable(final ResultSet remoteTables, final List<TableMetadata> translatedTables,
final List<String> selectedTables) throws SQLException {
private List<TableMetadata> extractTableMetadata(final ResultSet remoteTables, final List<String> selectedTables)
throws SQLException {
final List<TableMetadata> mappedTables = new ArrayList<>();
do {
final Optional<TableMetadata> tableMetadata = getTableMetadata(remoteTables, selectedTables);
tableMetadata.ifPresent(mappedTables::add);
validateMappedTablesListSize(mappedTables);
} while (remoteTables.next());
return mappedTables;
}

private Optional<TableMetadata> getTableMetadata(final ResultSet remoteTables, final List<String> selectedTables)
throws SQLException {
final String tableName = readTableName(remoteTables);
if (isTableIncludedByMapping(tableName)) {
mapSupportedTables(remoteTables, translatedTables, selectedTables, tableName);
} else {
skipUnsupportedTable(tableName);
if (isTableSupported(selectedTables, tableName)) {
return getTableMetadata(remoteTables, tableName);
}
return Optional.empty();
}

protected String readTableName(final ResultSet remoteTables) throws SQLException {
return remoteTables.getString(NAME_COLUMN);
}

private void mapSupportedTables(final ResultSet remoteTables, final List<TableMetadata> translatedTables,
final List<String> selectedTables, final String tableName) throws SQLException {
if (isTableSelected(tableName, selectedTables)) {
mapOrSkipSelectedTable(remoteTables, translatedTables, tableName);
private Optional<TableMetadata> getTableMetadata(final ResultSet remoteTables, final String tableName)
throws SQLException {
final TableMetadata tableMetadata = mapTable(remoteTables, tableName);
if (tableHasColumns(tableMetadata)) {
LOGGER.finer(() -> "Read table metadata: " + tableMetadata.describe());
return Optional.of(tableMetadata);
} else {
LOGGER.fine(() -> "Skipping filtered out table \"" + tableName + "\" when mapping remote metadata.");
logSkippingTableWithEmptyColumns(tableName);
return Optional.empty();
}
}

@Override
public boolean isTableIncludedByMapping(final String tableName) {
return true;
protected TableMetadata mapTable(final ResultSet table, final String tableName) throws SQLException {
final String comment = Optional.ofNullable(readComment(table)).orElse("");
final List<ColumnMetadata> columns = this.columnMetadataReader.mapColumns(tableName);
return new TableMetadata(adjustIdentifierCase(tableName), DEFAULT_TABLE_ADAPTER_NOTES, columns, comment);
}

protected boolean isTableSelected(final String tableName, final List<String> selectedTables) {
return (selectedTables == null) || selectedTables.isEmpty() || selectedTables.contains(tableName);
private String adjustIdentifierCase(final String tableName) {
return this.identifierConverter.convert(tableName);
}

protected void mapOrSkipSelectedTable(final ResultSet remoteTables, final List<TableMetadata> translatedTables,
final String tableName) throws SQLException {
if (isTableFilteredOut(tableName)) {
skipFilteredTable(tableName);
} else {
mapTableNotFilteredOut(remoteTables, translatedTables, tableName);
}
protected String readComment(final ResultSet remoteTables) throws SQLException {
return remoteTables.getString(REMARKS_COLUMN);
}

private boolean isTableFilteredOut(final String tableName) {
final List<String> filteredTables = this.properties.getFilteredTables();
if (filteredTables.isEmpty()) {
return false;
} else {
return !filteredTables.contains(tableName);
}
protected boolean tableHasColumns(final TableMetadata tableMetadata) {
return !tableMetadata.getColumns().isEmpty();
}

protected void skipFilteredTable(final String tableName) {
LOGGER.fine(
() -> "Skipping table \"" + tableName + "\" when mapping remote data due to user-defined table filter");
private void validateMappedTablesListSize(final List<TableMetadata> selectedTables) {
if (selectedTables.size() > DEFAULT_MAX_MAPPED_TABLE_LIST_SIZE) {
throw new RemoteMetadataReaderException(
"The size of the list of the selected tables exceeded the default allowed maximum: "
+ DEFAULT_MAX_MAPPED_TABLE_LIST_SIZE + ". "
+ "Please, use the TABLE_FILTER property to define the list of tables you need.");
}
}

protected void mapTableNotFilteredOut(final ResultSet remoteTables, final List<TableMetadata> translatedTables,
final String tableName) throws SQLException {
final TableMetadata tableMetadata = mapTable(remoteTables, tableName);
if (tableMetadata.getColumns().isEmpty()) {
skipTableWithEmptyColumns(tableName);
protected boolean isTableSupported(final List<String> selectedTables, final String tableName) {
if (isTableIncludedByMapping(tableName)) {
return isTableSelected(selectedTables, tableName);
} else {
addMappedTable(translatedTables, tableMetadata);
logSkippingUnsupportedTable(tableName);
return false;
}
}

protected void skipTableWithEmptyColumns(final String tableName) {
LOGGER.fine(() -> "Not mapping table \"" + tableName + "\" because it has no columns."
+ " This can happen if the view containing the columns is invalid"
+ " or if the Virtual Schema adapter does not support mapping the column types.");
@Override
public boolean isTableIncludedByMapping(final String tableName) {
return true;
}

protected void addMappedTable(final List<TableMetadata> translatedTables, final TableMetadata tableMetadata) {
LOGGER.finer(() -> "Read table metadata: " + tableMetadata.describe());
translatedTables.add(tableMetadata);
protected void logSkippingUnsupportedTable(final String tableName) {
LOGGER.fine(() -> "Skipping unsupported table \"" + tableName + "\" when mapping remote metadata.");
}

protected TableMetadata mapTable(final ResultSet table, final String tableName) throws SQLException {
final String comment = Optional.ofNullable(readComment(table)).orElse("");
final List<ColumnMetadata> columns = this.columnMetadataReader.mapColumns(tableName);
final String adapterNotes = DEFAULT_TABLE_ADAPTER_NOTES;
return new TableMetadata(adjustIdentifierCase(tableName), adapterNotes, columns, comment);
private boolean isTableSelected(final List<String> selectedTables, final String tableName) {
if (checkIfTableIsSelected(tableName, selectedTables)) {
return isTableIncludedByFilter(tableName);
} else {
LOGGER.fine(() -> "Skipping filtered out table \"" + tableName + "\" when mapping remote metadata.");
return false;
}
}

private String adjustIdentifierCase(final String tableName) {
return this.identifierConverter.convert(tableName);
protected boolean checkIfTableIsSelected(final String tableName, final List<String> selectedTables) {
return (selectedTables == null) || selectedTables.isEmpty() || selectedTables.contains(tableName);
}

protected String readTableName(final ResultSet remoteTables) throws SQLException {
return remoteTables.getString(NAME_COLUMN);
protected boolean isTableIncludedByFilter(final String tableName) {
final List<String> filteredTables = this.properties.getFilteredTables();
if (filteredTables.isEmpty() || filteredTables.contains(tableName)) {
return true;
} else {
logSkippingFilteredTable(tableName);
return false;
}
}

protected String readComment(final ResultSet remoteTables) throws SQLException {
return remoteTables.getString(REMARKS_COLUMN);
protected void logSkippingFilteredTable(final String tableName) {
LOGGER.fine(
() -> "Skipping table \"" + tableName + "\" when mapping remote data due to user-defined table filter");
}

protected boolean isUnquotedIdentifier(final String identifier) {
return UNQUOTED_IDENTIFIER_PATTERN.matcher(identifier).matches();
protected void logSkippingTableWithEmptyColumns(final String tableName) {
LOGGER.fine(() -> "Not mapping table \"" + tableName + "\" because it has no columns."
+ " This can happen if the view containing the columns is invalid"
+ " or if the Virtual Schema adapter does not support mapping the column types.");
}

protected void skipUnsupportedTable(final String tableName) {
LOGGER.fine(() -> "Skipping unsupported table \"" + tableName + "\" when mapping remote metadata.");
protected boolean isUnquotedIdentifier(final String identifier) {
return UNQUOTED_IDENTIFIER_PATTERN.matcher(identifier).matches();
}
}
}

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