use of org.apache.drill.exec.planner.sql.parser.SqlDescribeTable in project drill by apache.
the class DescribeTableHandler method rewrite.
/** Rewrite the parse tree as SELECT ... FROM INFORMATION_SCHEMA.COLUMNS ... */
@Override
public SqlNode rewrite(SqlNode sqlNode) throws RelConversionException, ForemanSetupException {
SqlDescribeTable node = unwrap(sqlNode, SqlDescribeTable.class);
try {
List<SqlNode> selectList = ImmutableList.of((SqlNode) new SqlIdentifier(COLS_COL_COLUMN_NAME, SqlParserPos.ZERO), new SqlIdentifier(COLS_COL_DATA_TYPE, SqlParserPos.ZERO), new SqlIdentifier(COLS_COL_IS_NULLABLE, SqlParserPos.ZERO));
SqlNode fromClause = new SqlIdentifier(ImmutableList.of(IS_SCHEMA_NAME, TAB_COLUMNS), null, SqlParserPos.ZERO, null);
final SqlIdentifier table = node.getTable();
final SchemaPlus defaultSchema = config.getConverter().getDefaultSchema();
final List<String> schemaPathGivenInCmd = Util.skipLast(table.names);
final SchemaPlus schema = SchemaUtilites.findSchema(defaultSchema, schemaPathGivenInCmd);
final String charset = Util.getDefaultCharset().name();
if (schema == null) {
SchemaUtilites.throwSchemaNotFoundException(defaultSchema, SchemaUtilites.SCHEMA_PATH_JOINER.join(schemaPathGivenInCmd));
}
if (SchemaUtilites.isRootSchema(schema)) {
throw UserException.validationError().message("No schema selected.").build(logger);
}
final String tableName = Util.last(table.names);
// find resolved schema path
final String schemaPath = SchemaUtilites.unwrapAsDrillSchemaInstance(schema).getFullSchemaName();
if (schema.getTable(tableName) == null) {
throw UserException.validationError().message("Unknown table [%s] in schema [%s]", tableName, schemaPath).build(logger);
}
SqlNode schemaCondition = null;
if (!SchemaUtilites.isRootSchema(schema)) {
schemaCondition = DrillParserUtil.createCondition(new SqlIdentifier(SHRD_COL_TABLE_SCHEMA, SqlParserPos.ZERO), SqlStdOperatorTable.EQUALS, SqlLiteral.createCharString(schemaPath, charset, SqlParserPos.ZERO));
}
SqlNode where = DrillParserUtil.createCondition(new SqlIdentifier(SHRD_COL_TABLE_NAME, SqlParserPos.ZERO), SqlStdOperatorTable.EQUALS, SqlLiteral.createCharString(tableName, charset, SqlParserPos.ZERO));
where = DrillParserUtil.createCondition(schemaCondition, SqlStdOperatorTable.AND, where);
SqlNode columnFilter = null;
if (node.getColumn() != null) {
columnFilter = DrillParserUtil.createCondition(new SqlIdentifier(COLS_COL_COLUMN_NAME, SqlParserPos.ZERO), SqlStdOperatorTable.EQUALS, SqlLiteral.createCharString(node.getColumn().toString(), charset, SqlParserPos.ZERO));
} else if (node.getColumnQualifier() != null) {
columnFilter = DrillParserUtil.createCondition(new SqlIdentifier(COLS_COL_COLUMN_NAME, SqlParserPos.ZERO), SqlStdOperatorTable.LIKE, node.getColumnQualifier());
}
where = DrillParserUtil.createCondition(where, SqlStdOperatorTable.AND, columnFilter);
return new SqlSelect(SqlParserPos.ZERO, null, new SqlNodeList(selectList, SqlParserPos.ZERO), fromClause, where, null, null, null, null, null, null);
} catch (Exception ex) {
throw UserException.planError(ex).message("Error while rewriting DESCRIBE query: %d", ex.getMessage()).build(logger);
}
}
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