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Merge pull request #260 from eyalleshem/single_tables_in_parens

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[snowflake] Support `FROM (table_name) alias`
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Nickolay Ponomarev 2020-10-13 09:59:38 +03:00 • committed by GitHub
commit 929fc6764f
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12 changed files with 239 additions and 88 deletions
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src/parser.rs
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@ -2158,14 +2158,58 @@ impl<'a> Parser<'a> {
// recently consumed does not start a derived table (cases 1, 2, or 4).
// `maybe_parse` will ignore such an error and rewind to be after the opening '('.
// Inside the parentheses we expect to find a table factor
// followed by some joins or another level of nesting.
let table_and_joins = self.parse_table_and_joins()?;
self.expect_token(&Token::RParen)?;
// The SQL spec prohibits derived and bare tables from appearing
// alone in parentheses. We don't enforce this as some databases
// (e.g. Snowflake) allow such syntax.
Ok(TableFactor::NestedJoin(Box::new(table_and_joins)))
// Inside the parentheses we expect to find an (A) table factor
// followed by some joins or (B) another level of nesting.
let mut table_and_joins = self.parse_table_and_joins()?;
if !table_and_joins.joins.is_empty() {
self.expect_token(&Token::RParen)?;
Ok(TableFactor::NestedJoin(Box::new(table_and_joins))) // (A)
} else if let TableFactor::NestedJoin(_) = &table_and_joins.relation {
// (B): `table_and_joins` (what we found inside the parentheses)
// is a nested join `(foo JOIN bar)`, not followed by other joins.
self.expect_token(&Token::RParen)?;
Ok(TableFactor::NestedJoin(Box::new(table_and_joins)))
} else if dialect_of!(self is SnowflakeDialect | GenericDialect) {
// Dialect-specific behavior: Snowflake diverges from the
// standard and from most of the other implementations by
// allowing extra parentheses not only around a join (B), but
// around lone table names (e.g. `FROM (mytable [AS alias])`)
// and around derived tables (e.g. `FROM ((SELECT ...)
// [AS alias])`) as well.
self.expect_token(&Token::RParen)?;
if let Some(outer_alias) =
self.parse_optional_table_alias(keywords::RESERVED_FOR_TABLE_ALIAS)?
{
// Snowflake also allows specifying an alias *after* parens
// e.g. `FROM (mytable) AS alias`
match &mut table_and_joins.relation {
TableFactor::Derived { alias, .. }
| TableFactor::Table { alias, .. }
| TableFactor::TableFunction { alias, .. } => {
// but not `FROM (mytable AS alias1) AS alias2`.
if let Some(inner_alias) = alias {
return Err(ParserError::ParserError(format!(
"duplicate alias {}",
inner_alias
)));
}
// Act as if the alias was specified normally next
// to the table name: `(mytable) AS alias` ->
// `(mytable AS alias)`
alias.replace(outer_alias);
}
TableFactor::NestedJoin(_) => unreachable!(),
};
}
// Do not store the extra set of parens in the AST
Ok(table_and_joins.relation)
} else {
// The SQL spec prohibits derived tables and bare tables from
// appearing alone in parentheses (e.g. `FROM (mytable)`)
self.expected("joined table", self.peek_token())
}
} else {
let name = self.parse_object_name()?;
// Postgres, MSSQL: table-valued functions: