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Jan 22, 2021
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updated/PLUGIN-296 #457

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3 changes: 2 additions & 1 deletion docs/Spanner-batchsource.md
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Original file line number Diff line number Diff line change
Expand Up @@ -52,4 +52,5 @@ The actual number of partitions returned may be smaller or larger than this maxi
This is only a hint. The actual size of each partition may be smaller or larger than this size request.
More information about partition options can be found at https://cloud.google.com/spanner/docs/reference/rest/v1/PartitionOptions

**Schema**: Schema of the Spanner table to read.
**Schema**: Schema of the Spanner table to read. When *import query* is used and column name is not in the metadata table
the field will be nullable.
150 changes: 133 additions & 17 deletions src/main/java/io/cdap/plugin/gcp/spanner/source/SpannerSource.java
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Expand Up @@ -52,6 +52,7 @@
import io.cdap.plugin.gcp.spanner.SpannerArrayConstants;
import io.cdap.plugin.gcp.spanner.SpannerConstants;
import io.cdap.plugin.gcp.spanner.common.SpannerUtil;
import org.apache.commons.lang3.StringUtils;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.io.NullWritable;
import org.slf4j.Logger;
Expand All @@ -62,8 +63,11 @@
import java.io.ObjectOutputStream;
import java.util.ArrayList;
import java.util.Base64;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.concurrent.TimeUnit;
import java.util.regex.Pattern;
import java.util.stream.Collectors;
import javax.annotation.Nullable;

Expand All @@ -82,6 +86,8 @@ public class SpannerSource extends BatchSource<NullWritable, ResultSet, Structur
private static final Statement.Builder SCHEMA_STATEMENT_BUILDER = Statement.newBuilder(
String.format("SELECT t.column_name,t.spanner_type, t.is_nullable FROM information_schema.columns AS t WHERE " +
" t.table_catalog = '' AND t.table_schema = '' AND t.table_name = @%s", TABLE_NAME));
private static final String LIMIT = "limit";

public static final String NAME = "Spanner";
private final SpannerSourceConfig config;
private Schema schema;
Expand Down Expand Up @@ -243,26 +249,55 @@ private Schema getSchema(FailureCollector collector) {
projectId)) {
DatabaseClient databaseClient =
spanner.getDatabaseClient(DatabaseId.of(projectId, config.instance, config.database));
Statement getTableSchemaStatement = SCHEMA_STATEMENT_BUILDER.bind(TABLE_NAME).to(config.table).build();
try (ResultSet resultSet = databaseClient.singleUse().executeQuery(getTableSchemaStatement)) {
List<Schema.Field> schemaFields = new ArrayList<>();
while (resultSet.next()) {
String columnName = resultSet.getString("column_name");
String spannerType = resultSet.getString("spanner_type");
String nullable = resultSet.getString("is_nullable");
boolean isNullable = "YES".equals(nullable);
Schema typeSchema = parseSchemaFromSpannerTypeString(columnName, spannerType, collector);
if (typeSchema == null) {
// this means there were failures added to failure collector. Continue to collect more failures
continue;
if (Strings.isNullOrEmpty(config.importQuery)) {
Statement getTableSchemaStatement = SCHEMA_STATEMENT_BUILDER.bind(TABLE_NAME).to(config.table).build();
try (ResultSet resultSet = databaseClient.singleUse().executeQuery(getTableSchemaStatement)) {
List<Schema.Field> schemaFields = new ArrayList<>();
while (resultSet.next()) {
String columnName = resultSet.getString("column_name");
String spannerType = resultSet.getString("spanner_type");
String nullable = resultSet.getString("is_nullable");
boolean isNullable = "YES".equals(nullable);
Schema typeSchema = parseSchemaFromSpannerTypeString(columnName, spannerType, collector);
if (typeSchema == null) {
// this means there were failures added to failure collector. Continue to collect more failures
continue;
}
Schema fieldSchema = isNullable ? Schema.nullableOf(typeSchema) : typeSchema;
schemaFields.add(Schema.Field.of(columnName, fieldSchema));
}
if (schemaFields.isEmpty() && !collector.getValidationFailures().isEmpty()) {
collector.getOrThrowException();
}
Schema fieldSchema = isNullable ? Schema.nullableOf(typeSchema) : typeSchema;
schemaFields.add(Schema.Field.of(columnName, fieldSchema));
return Schema.recordOf("outputSchema", schemaFields);
}
if (schemaFields.isEmpty() && !collector.getValidationFailures().isEmpty()) {
collector.getOrThrowException();
} else {
final Map<String, Boolean> nullableFields = getFieldsNullability(databaseClient);
Statement importQueryStatement = getStatementForOneRow(config.importQuery);
List<Schema.Field> schemaFields = new ArrayList<>();
try (ResultSet resultSet = databaseClient.singleUse().executeQuery(importQueryStatement)) {
while (resultSet.next()) {
final List<Type.StructField> structFields = resultSet.getCurrentRowAsStruct().getType().getStructFields();
for (Type.StructField structField : structFields) {
final Type fieldSpannerType = structField.getType();
final String columnName = structField.getName();
// there are cases when column name is not in metadata table such as "Select FirstName as name",
// so fallback is nullable
final boolean isNullable = nullableFields.getOrDefault(columnName, true);
final Schema typeSchema = parseSchemaFromSpannerType(fieldSpannerType, columnName, collector);
if (typeSchema == null) {
// this means there were failures added to failure collector. Continue to collect more failures
continue;
}
Schema fieldSchema = isNullable ? Schema.nullableOf(typeSchema) : typeSchema;
schemaFields.add(Schema.Field.of(columnName, fieldSchema));
}
}
if (schemaFields.isEmpty() && !collector.getValidationFailures().isEmpty()) {
collector.getOrThrowException();
}
return Schema.recordOf("outputSchema", schemaFields);
}
return Schema.recordOf("outputSchema", schemaFields);
}
} catch (IOException e) {
collector.addFailure("Unable to get Spanner Client: " + e.getMessage(), null)
Expand All @@ -274,6 +309,22 @@ private Schema getSchema(FailureCollector collector) {

}

private Statement getStatementForOneRow(String importQuery) {
String query;
// Matches any String containing the word 'limit' followed by a number
// ex: SELECT NAME FROM TABLE LIMIT 15
String regex = "^(?:[^;']|(?:'[^']+'))+ LIMIT +\\d+(.*)";
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@rmstar rmstar Jan 20, 2021

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Please add a comment that explains what this regex matches.

Pattern pattern = Pattern.compile(regex, Pattern.MULTILINE | Pattern.CASE_INSENSITIVE);
if (pattern.matcher(importQuery).matches()) {
int index = StringUtils.lastIndexOf(importQuery, LIMIT);
String substringToReplace = importQuery.substring(index);
query = importQuery.replace(substringToReplace, "limit 1");
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@rmstar rmstar Jan 19, 2021

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This can break in some corner cases where the table name contains "limit" substring. For example something like SELECT <columns> from limited.
Can you make sure we only replace "limit < number >" with "limit 1".

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@ardian4 ardian4 Jan 20, 2021

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Done

} else {
query = String.format("%s limit 1", importQuery);
}
return Statement.newBuilder(query).build();
}

@Nullable
private Schema parseSchemaFromSpannerTypeString(String columnName,
String spannerType, FailureCollector collector) {
Expand Down Expand Up @@ -323,4 +374,69 @@ private Schema parseSchemaFromSpannerTypeString(String columnName,
}
return null;
}

@Nullable
Schema parseSchemaFromSpannerType(Type spannerType, String columnName, FailureCollector collector) {
final Type.Code code = spannerType.getCode();

if (code == Type.Code.ARRAY) {
final Type arrayElementType = spannerType.getArrayElementType();
final Type.Code arrayElementTypeCode = arrayElementType.getCode();
switch (arrayElementTypeCode) {
case BOOL:
return Schema.arrayOf(Schema.of(Schema.Type.BOOLEAN));
case INT64:
return Schema.arrayOf(Schema.of(Schema.Type.LONG));
case FLOAT64:
return Schema.arrayOf(Schema.of(Schema.Type.DOUBLE));
case STRING:
return Schema.arrayOf(Schema.of(Schema.Type.STRING));
case BYTES:
return Schema.arrayOf(Schema.of(Schema.Type.BYTES));
case TIMESTAMP:
return Schema.arrayOf(Schema.of(Schema.LogicalType.TIMESTAMP_MICROS));
case DATE:
return Schema.arrayOf(Schema.of(Schema.LogicalType.DATE));
default:
collector.addFailure(String.format("Column '%s' has unsupported type '%s'.", columnName, spannerType), null);
return null;
}
} else {
switch (code) {
case BOOL:
return Schema.of(Schema.Type.BOOLEAN);
case INT64:
return Schema.of(Schema.Type.LONG);
case FLOAT64:
return Schema.of(Schema.Type.DOUBLE);
case STRING:
return Schema.of(Schema.Type.STRING);
case BYTES:
return Schema.of(Schema.Type.BYTES);
case TIMESTAMP:
return Schema.of(Schema.LogicalType.TIMESTAMP_MICROS);
case DATE:
return Schema.of(Schema.LogicalType.DATE);
default:
collector.addFailure(String.format("Column '%s' has unsupported type '%s'.", columnName, spannerType), null);
return null;
}
}
}

/** Get from table metadata nullability for each field
* @param databaseClient Database Client
* @return Map where key is field name and value is nullability true or false
*/
private Map<String, Boolean> getFieldsNullability(DatabaseClient databaseClient) {
Statement tableMetadataStatement = SCHEMA_STATEMENT_BUILDER.bind(TABLE_NAME).to(config.table).build();
Map<String, Boolean> nullableState = new HashMap<>();
ResultSet resultSet = databaseClient.singleUse().executeQuery(tableMetadataStatement);
while (resultSet.next()) {
String columnName = resultSet.getString("column_name");
String nullable = resultSet.getString("is_nullable");
nullableState.put(columnName, "YES".equals(nullable));
}
return nullableState;
}
}