vantage_sql/primitives/
json_extract.rs

1use std::fmt::{Debug, Display};
2
3use vantage_core::util::IntoVec;
4use vantage_expressions::{Expression, Expressive, ExpressiveEnum};
5
6/// Vendor-aware JSON field extraction.
7///
8/// Accepts a single field or a path of fields. For multi-level paths,
9/// intermediate steps use the JSON-object accessor and the final step
10/// extracts as text.
11///
12/// Renders as (extract as text by default):
13/// - **SQLite:**     `JSON_EXTRACT("col", '$.field')`
14/// - **MySQL:**      `` JSON_UNQUOTE(JSON_EXTRACT(`col`, '$.field')) ``
15/// - **PostgreSQL:** `"col" ->> 'field'` or `"col" -> 'a' ->> 'b'`
16///
17/// With `.as_json()` — return raw JSON instead of text:
18/// - **MySQL:**      `` JSON_EXTRACT(`col`, '$.field') ``
19/// - **PostgreSQL:** `"col" -> 'field'`
20///
21/// # Examples
22///
23/// ```ignore
24/// // Single field
25/// JsonExtract::new(ident("metadata"), "color")
26///
27/// // Nested path
28/// JsonExtract::new(ident("metadata"), ["specs", "voltage"])
29/// ```
30#[derive(Debug, Clone)]
31pub struct JsonExtract<T: Debug + Display + Clone> {
32    source: Expression<T>,
33    path: Vec<String>,
34    /// When true, return the raw JSON value instead of extracting as text.
35    /// Affects MySQL (drops `JSON_UNQUOTE`) and PostgreSQL (all `->` vs final `->>`)
36    as_json: bool,
37}
38
39impl<T: Debug + Display + Clone> JsonExtract<T> {
40    pub fn new(source: impl Expressive<T>, path: impl IntoVec<String>) -> Self {
41        Self {
42            source: source.expr(),
43            path: path.into_vec(),
44            as_json: false,
45        }
46    }
47
48    /// Return raw JSON instead of text (no `JSON_UNQUOTE` in MySQL, `->` in PG).
49    pub fn as_json(mut self) -> Self {
50        self.as_json = true;
51        self
52    }
53}
54
55/// Shorthand for `JsonExtract::new(source, path)`.
56pub fn json_extract<T: Debug + Display + Clone>(
57    source: impl Expressive<T>,
58    path: impl IntoVec<String>,
59) -> JsonExtract<T> {
60    JsonExtract::new(source, path)
61}
62
63/// Helper: create an inline SQL literal (not a bind parameter).
64fn sql_lit<T: Debug + Display + Clone>(s: &str) -> Expression<T> {
65    let escaped = s.replace('\'', "''");
66    Expression::new(format!("'{escaped}'"), vec![])
67}
68
69#[cfg(feature = "sqlite")]
70impl Expressive<crate::sqlite::types::AnySqliteType>
71    for JsonExtract<crate::sqlite::types::AnySqliteType>
72{
73    fn expr(&self) -> Expression<crate::sqlite::types::AnySqliteType> {
74        let json_path = format!("$.{}", self.path.join("."));
75        Expression::new(
76            "JSON_EXTRACT({}, {})",
77            vec![
78                ExpressiveEnum::Nested(self.source.clone()),
79                ExpressiveEnum::Nested(sql_lit(&json_path)),
80            ],
81        )
82    }
83}
84
85// The function forms of MySQL's `->>` / `->`; MariaDB has only the functions.
86
87#[cfg(feature = "mysql")]
88impl Expressive<crate::mysql::types::AnyMysqlType>
89    for JsonExtract<crate::mysql::types::AnyMysqlType>
90{
91    fn expr(&self) -> Expression<crate::mysql::types::AnyMysqlType> {
92        let json_path = format!("$.{}", self.path.join("."));
93        let template = if self.as_json {
94            "JSON_EXTRACT({}, {})"
95        } else {
96            "JSON_UNQUOTE(JSON_EXTRACT({}, {}))"
97        };
98        Expression::new(
99            template,
100            vec![
101                ExpressiveEnum::Nested(self.source.clone()),
102                ExpressiveEnum::Nested(sql_lit(&json_path)),
103            ],
104        )
105    }
106}
107
108#[cfg(feature = "postgres")]
109impl Expressive<crate::postgres::types::AnyPostgresType>
110    for JsonExtract<crate::postgres::types::AnyPostgresType>
111{
112    fn expr(&self) -> Expression<crate::postgres::types::AnyPostgresType> {
113        // Build chain: source -> 'a' -> 'b' ->> 'last'
114        // All intermediate steps use -> (returns jsonb), final step uses ->> (returns text)
115        assert!(
116            !self.path.is_empty(),
117            "JsonExtract requires at least one path segment"
118        );
119        let mut current = self.source.clone();
120        let last = self.path.len() - 1;
121
122        for (i, field) in self.path.iter().enumerate() {
123            let op = if i == last && !self.as_json {
124                " ->> "
125            } else {
126                " -> "
127            };
128            current = Expression::new(
129                format!("{{}}{op}{{}}"),
130                vec![
131                    ExpressiveEnum::Nested(current),
132                    ExpressiveEnum::Nested(sql_lit(field)),
133                ],
134            );
135        }
136
137        current
138    }
139}
vantage_sql/primitives/json_extract.rs

vantage_sql/primitives/
json_extract.rs
