## Coverage Report

#### Created: 2024-10-13 08:39

    /Users/andrewlamb/Software/datafusion/datafusion/expr/src/var_provider.rs

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    // Licensed to the Apache Software Foundation (ASF) under one
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    // or more contributor license agreements.  See the NOTICE file
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    // distributed with this work for additional information
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    // regarding copyright ownership.  The ASF licenses this file
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    // to you under the Apache License, Version 2.0 (the
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    // "License"); you may not use this file except in compliance
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    // with the License.  You may obtain a copy of the License at
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    //
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    //   http://www.apache.org/licenses/LICENSE-2.0
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    //
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    // Unless required by applicable law or agreed to in writing,
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    // software distributed under the License is distributed on an
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    // "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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    // KIND, either express or implied.  See the License for the
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    // specific language governing permissions and limitations
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    // under the License.
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    //! Variable provider
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    use arrow::datatypes::DataType;
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    use datafusion_common::{Result, ScalarValue};
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    /// Variable type, system/user defined
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    #[derive(Debug, Clone, PartialEq, Eq, Hash)]
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    pub enum VarType {
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        /// System variable, like @@version
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        System,
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        /// User defined variable, like @name
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        UserDefined,
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    }
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    /// A var provider for `@variable` and `@@variable` runtime values.
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    pub trait VarProvider: std::fmt::Debug {
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        /// Get variable value
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        fn get_value(&self, var_names: Vec<String>) -> Result<ScalarValue>;
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        /// Return the type of the given variable
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        fn get_type(&self, var_names: &[String]) -> Option<DataType>;
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    }
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    pub fn is_system_variables(variable_names: &[String]) -> bool {
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        !variable_names.is_empty() && variable_names[0].get(0..2) == Some("@@")
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    }
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    #[cfg(test)]
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    mod test {
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        use super::*;
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        #[test]
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        fn test_is_system_variables() {
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            assert!(!is_system_variables(&["N".into(), "\"\"".into()]));
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            assert!(is_system_variables(&["@@D".into(), "F".into(), "J".into()]));
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            assert!(!is_system_variables(&[
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                "J".into(),
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                "@@F".into(),
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                "K".into()
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            ]));
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            assert!(!is_system_variables(&[]));
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            assert!(is_system_variables(&[
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                "@@longvariablenamethatIdontknowhwyanyonewoulduse".into()
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            ]));
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            assert!(!is_system_variables(&["@F".into()]));
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        }
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    }