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Add support for generated virtual columns with expression #1051

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Merged
merged 6 commits into from
Nov 22, 2023
Merged

Add support for generated virtual columns with expression #1051

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9618cda
Add support for generated virtual columns with expression
takluyver Nov 19, 2023
05ac5bc
Extend generated column tests for SQLite & add for MySQL
takluyver Nov 20, 2023
ec986b0
Remove outdated comment
takluyver Nov 20, 2023
f0d0f5b
Remove redundant check in tests
takluyver Nov 21, 2023
6d69a43
Preserve presence/absence of VIRTUAL for generated columns
takluyver Nov 22, 2023
2887501
Remove some leftover debugging
takluyver Nov 22, 2023
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32 changes: 19 additions & 13 deletions src/ast/ddl.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -641,20 +641,26 @@ impl fmt::Display for ColumnOption {
generation_expr,
} => match generated_as {
GeneratedAs::Always => {
write!(f, "GENERATED ALWAYS AS IDENTITY")?;
if sequence_options.is_some() {
let so = sequence_options.as_ref().unwrap();
if !so.is_empty() {
write!(f, " (")?;
}
for sequence_option in so {
write!(f, "{sequence_option}")?;
}
if !so.is_empty() {
write!(f, " )")?;
if let Some(expr) = generation_expr {
// Like SQLite, MySQL - expr evaluated on read
write!(f, "GENERATED ALWAYS AS ({expr}) VIRTUAL")
} else {
// Like Postgres - generated from sequence
write!(f, "GENERATED ALWAYS AS IDENTITY")?;
if sequence_options.is_some() {
let so = sequence_options.as_ref().unwrap();
if !so.is_empty() {
write!(f, " (")?;
}
for sequence_option in so {
write!(f, "{sequence_option}")?;
}
if !so.is_empty() {
write!(f, " )")?;
}
}
Ok(())
}
Ok(())
}
GeneratedAs::ByDefault => {
write!(f, "GENERATED BY DEFAULT AS IDENTITY")?;
Expand Down Expand Up @@ -682,7 +688,7 @@ impl fmt::Display for ColumnOption {
}

/// `GeneratedAs`s are modifiers that follow a column option in a `generated`.
/// 'ExpStored' is PostgreSQL specific
/// 'ExpStored' is used for a column generated from an expression and stored.
#[derive(Debug, Clone, PartialEq, PartialOrd, Eq, Ord, Hash)]
#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
#[cfg_attr(feature = "visitor", derive(Visit, VisitMut))]
Expand Down
13 changes: 11 additions & 2 deletions src/parser/mod.rs
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Expand Up @@ -4252,9 +4252,18 @@ impl<'a> Parser<'a> {
if self.expect_token(&Token::LParen).is_ok() {
let expr = self.parse_expr()?;
self.expect_token(&Token::RParen)?;
let _ = self.parse_keywords(&[Keyword::STORED]);
let gen_as = if self.parse_keywords(&[Keyword::STORED]) {
Ok(GeneratedAs::ExpStored)
} else if dialect_of!(self is PostgreSqlDialect) {
// Postgres' AS IDENTITY branches are above, this one needs STORED
self.expected("STORED", self.peek_token())
} else {
let _ = self.parse_keywords(&[Keyword::VIRTUAL]);
Ok(GeneratedAs::Always)
}?;

Ok(Some(ColumnOption::Generated {
generated_as: GeneratedAs::ExpStored,
generated_as: gen_as,
sequence_options: None,
generation_expr: Some(expr),
}))
Expand Down
11 changes: 11 additions & 0 deletions tests/sqlparser_mysql.rs
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Expand Up @@ -507,6 +507,17 @@ fn parse_create_table_comment_character_set() {
}
}

#[test]
fn parse_create_table_gencol() {
let sql_default = "CREATE TABLE t1 (a INT, b INT GENERATED ALWAYS AS (a * 2))";
let sql_virt = "CREATE TABLE t1 (a INT, b INT GENERATED ALWAYS AS (a * 2) VIRTUAL)";
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What do you think about adding additional support to the AST so you can recover the original SQL --- as implemented now this change will not permit people to know when the original query had VIRTUAL or not

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Virtual is the default, so adding the marker doesn't make a logical difference (at least in the databases I found that support this). Elsewhere in the tests, it looks like you don't preserve differences like this - e.g. SHOW COLUMNS vs SHOW FIELDS in the MySQL tests. But if you'd like to preserve this one, I'm happy to do that. 🙂

If so, I would probably introduce an enum called something like GenExpressionQualifier (though that's an ugly name...), which could be None, Virtual or Stored. The Stored option would then be redundant with GeneratedAs::ExpStored.

(For my next PR, I'm planning to make the GENERATED ALWAYS keywords optional - as they are in MySQL and SQLite. Let me know if you want the presence or absence of those to be preserved too.)

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Elsewhere in the tests, it looks like you don't preserve differences like this - e.g. SHOW COLUMNS vs SHOW FIELDS in the MySQL tests. But if you'd like to preserve this one, I'm happy to do that. 🙂

Yes, it is true that this crate is not always consistent. However, for newly added code let's try and preserve the ability to round trip the AST (though I see there is no note describing that detail on https://github.com/sqlparser-rs/sqlparser-rs -- I will try and add a note when I have time)

Let me know if you want the presence or absence of those to be preserved too.)

yes, please

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OK, the latest commit (6d69a43) preserves the distinction between VIRTUAL, STORED and no qualifier. As I mentioned, that does mean there are two fields which both record if STORED was used. That's not so tidy, but it preserves compatibility for any code that's checking for GeneratedAs::ExpStored.

I've called the new field & enum generation_expr_mode & GeneratedExpressionMode, which are both quite a mouthful. Let me know if you have a better name for this. 🙂

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filed #1052 to document this property

mysql_and_generic().verified_stmt(sql_virt);
mysql_and_generic().one_statement_parses_to(sql_default, sql_virt);

let sql_stored = "CREATE TABLE t1 (a INT, b INT GENERATED ALWAYS AS (a * 2) STORED)";
mysql_and_generic().verified_stmt(sql_stored);
}

#[test]
fn parse_quote_identifiers() {
let sql = "CREATE TABLE `PRIMARY` (`BEGIN` INT PRIMARY KEY)";
Expand Down
12 changes: 11 additions & 1 deletion tests/sqlparser_sqlite.rs
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Expand Up @@ -205,6 +205,17 @@ fn parse_create_sqlite_quote() {
}
}

#[test]
fn parse_create_table_gencol() {
let sql_default = "CREATE TABLE t1 (a INT, b INT GENERATED ALWAYS AS (a * 2))";
let sql_virt = "CREATE TABLE t1 (a INT, b INT GENERATED ALWAYS AS (a * 2) VIRTUAL)";
sqlite_and_generic().verified_stmt(sql_virt);
sqlite_and_generic().one_statement_parses_to(sql_default, sql_virt);

let sql_stored = "CREATE TABLE t1 (a INT, b INT GENERATED ALWAYS AS (a * 2) STORED)";
sqlite_and_generic().verified_stmt(sql_stored);
}

#[test]
fn test_placeholder() {
// In postgres, this would be the absolute value operator '@' applied to the column 'xxx'
Expand Down Expand Up @@ -435,7 +446,6 @@ fn sqlite_with_options(options: ParserOptions) -> TestedDialects {

fn sqlite_and_generic() -> TestedDialects {
TestedDialects {
// we don't have a separate SQLite dialect, so test only the generic dialect for now
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👍 nice drive by cleanup

dialects: vec![Box::new(SQLiteDialect {}), Box::new(GenericDialect {})],
options: None,
}
Expand Down