spacetimedb_sql_parser_2/parser/
sub.rs

1//! The SpacetimeDB SQL subscription grammar
2//!
3//! ```ebnf
4//! query
5//!     = SELECT projection FROM relation [ WHERE predicate ]
6//!     ;
7//!
8//! projection
9//!     = STAR
10//!     | ident '.' STAR
11//!     ;
12//!
13//! relation
14//!     = table
15//!     | '(' query ')'
16//!     | relation [ [AS] ident ] { [INNER] JOIN relation [ [AS] ident ] ON predicate }
17//!     ;
18//!
19//! predicate
20//!     = expr
21//!     | predicate AND predicate
22//!     | predicate OR  predicate
23//!     ;
24//!
25//! expr
26//!     = literal
27//!     | ident
28//!     | field
29//!     | expr op expr
30//!     ;
31//!
32//! field
33//!     = ident '.' ident
34//!     ;
35//!
36//! op
37//!     = '='
38//!     | '<'
39//!     | '>'
40//!     | '<' '='
41//!     | '>' '='
42//!     | '!' '='
43//!     | '<' '>'
44//!     ;
45//!
46//! literal
47//!     = INTEGER
48//!     | FLOAT
49//!     | STRING
50//!     | HEX
51//!     | TRUE
52//!     | FALSE
53//!     ;
54//! ```
55
56use sqlparser::{
57    ast::{GroupByExpr, Query, Select, SetExpr, SetOperator, SetQuantifier, Statement},
58    dialect::PostgreSqlDialect,
59    parser::Parser,
60};
61
62use crate::ast::sub::{SqlAst, SqlSelect};
63
64use super::{
65    errors::{SqlUnsupported, SubscriptionUnsupported},
66    parse_expr_opt, parse_projection, RelParser, SqlParseResult,
67};
68
69/// Parse a SQL string
70pub fn parse_subscription(sql: &str) -> SqlParseResult<SqlAst> {
71    let mut stmts = Parser::parse_sql(&PostgreSqlDialect {}, sql)?;
72    if stmts.len() > 1 {
73        return Err(SqlUnsupported::MultiStatement.into());
74    }
75    parse_statement(stmts.swap_remove(0))
76}
77
78/// Parse a SQL query
79fn parse_statement(stmt: Statement) -> SqlParseResult<SqlAst> {
80    match stmt {
81        Statement::Query(query) => SubParser::parse_query(*query),
82        _ => Err(SubscriptionUnsupported::Dml.into()),
83    }
84}
85
86struct SubParser;
87
88impl RelParser for SubParser {
89    type Ast = SqlAst;
90
91    fn parse_query(query: Query) -> SqlParseResult<Self::Ast> {
92        match query {
93            Query {
94                with: None,
95                body,
96                order_by,
97                limit: None,
98                offset: None,
99                fetch: None,
100                locks,
101            } if order_by.is_empty() && locks.is_empty() => parse_set_op(*body),
102            _ => Err(SubscriptionUnsupported::feature(query).into()),
103        }
104    }
105}
106
107/// Parse a set operation
108fn parse_set_op(expr: SetExpr) -> SqlParseResult<SqlAst> {
109    match expr {
110        SetExpr::Query(query) => SubParser::parse_query(*query),
111        SetExpr::Select(select) => Ok(SqlAst::Select(parse_select(*select)?)),
112        SetExpr::SetOperation {
113            op: SetOperator::Union,
114            set_quantifier: SetQuantifier::All,
115            left,
116            right,
117        } => Ok(SqlAst::Union(
118            Box::new(parse_set_op(*left)?),
119            Box::new(parse_set_op(*right)?),
120        )),
121        SetExpr::SetOperation {
122            op: SetOperator::Except,
123            set_quantifier: SetQuantifier::All,
124            left,
125            right,
126        } => Ok(SqlAst::Minus(
127            Box::new(parse_set_op(*left)?),
128            Box::new(parse_set_op(*right)?),
129        )),
130        _ => Err(SqlUnsupported::SetOp(expr).into()),
131    }
132}
133
134// Parse a SELECT statement
135fn parse_select(select: Select) -> SqlParseResult<SqlSelect> {
136    match select {
137        Select {
138            distinct: None,
139            top: None,
140            projection,
141            into: None,
142            from,
143            lateral_views,
144            selection,
145            group_by: GroupByExpr::Expressions(exprs),
146            cluster_by,
147            distribute_by,
148            sort_by,
149            having: None,
150            named_window,
151            qualify: None,
152        } if lateral_views.is_empty()
153            && exprs.is_empty()
154            && cluster_by.is_empty()
155            && distribute_by.is_empty()
156            && sort_by.is_empty()
157            && named_window.is_empty() =>
158        {
159            Ok(SqlSelect {
160                from: SubParser::parse_from(from)?,
161                filter: parse_expr_opt(selection)?,
162                project: parse_projection(projection)?,
163            })
164        }
165        _ => Err(SubscriptionUnsupported::Select(select).into()),
166    }
167}
168
169#[cfg(test)]
170mod tests {
171    use crate::parser::sub::parse_subscription;
172
173    #[test]
174    fn unsupported() {
175        for sql in [
176            "delete from t",
177            "select distinct a from t",
178            "select * from (select * from t) join (select * from s) on a = b",
179        ] {
180            assert!(parse_subscription(sql).is_err());
181        }
182    }
183
184    #[test]
185    fn supported() {
186        for sql in [
187            "select * from t",
188            "select * from t where a = 1",
189            "select * from t where a <> 1",
190            "select * from t where a = 1 or a = 2",
191            "select * from t where a = 1 union all select * from t where a = 2",
192            "select * from (select * from t)",
193            "select * from (select t.* from t join s)",
194            "select * from (select t.* from t join s on t.c = s.d)",
195            "select * from (select a.* from t as a join s as b on a.c = b.d)",
196            "select * from (select t.* from (select * from t) t join (select * from s) s on s.id = t.id)",
197        ] {
198            assert!(parse_subscription(sql).is_ok());
199        }
200    }
201}
spacetimedb_sql_parser_2/parser/sub.rs

spacetimedb_sql_parser_2/parser/
sub.rs
