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use super::super::ScriptExecutor;
use crate::ast::WithCteStmt;
use crate::catalog::TableDef;
use crate::error::{DbError, StmtOutcome};
use crate::executor::context::ExecutionContext;
use crate::executor::result::QueryResult;
use crate::storage::StoredRow;
impl<'a> ScriptExecutor<'a> {
pub(crate) fn execute_with_cte(
&mut self,
stmt: WithCteStmt,
ctx: &mut ExecutionContext<'_>,
) -> Result<Option<QueryResult>, DbError> {
let old_ctes = ctx.row.ctes.clone();
for cte_def in &stmt.ctes {
if stmt.recursive {
// Recursive CTE logic
if let crate::ast::Statement::Dml(crate::ast::DmlStatement::SetOp(set_op)) =
&cte_def.query
{
if let crate::ast::SetOpKind::UnionAll = set_op.op {
let anchor_stmt = *set_op.left.clone();
let recursive_stmt = *set_op.right.clone();
// 2. Execute Anchor Member
let anchor_outcome = self.execute(anchor_stmt, ctx)?;
let result = match anchor_outcome {
StmtOutcome::Ok(Some(r)) => r,
StmtOutcome::Ok(None) => {
return Err(DbError::Execution(
"CTE anchor member must return a result set".into(),
))
}
// Propagate control flow
other => return other.into_result(),
};
let table_def = TableDef {
id: 0,
schema_id: 1,
schema_name: "dbo".to_string(),
name: cte_def.name.clone(),
columns: result
.columns
.iter()
.enumerate()
.map(|(i, name)| crate::catalog::ColumnDef {
id: (i + 1) as u32,
name: name.clone(),
data_type: result.column_types[i].clone(),
nullable: true,
primary_key: false,
unique: false,
identity: None,
default: None,
default_constraint_name: None,
computed_expr: None,
check: None,
check_constraint_name: None,
ansi_padding_on: true,
})
.collect(),
check_constraints: vec![],
foreign_keys: vec![],
};
let mut all_rows: Vec<StoredRow> = result
.rows
.iter()
.map(|v| StoredRow {
values: v.clone(),
deleted: false,
})
.collect();
let mut working_set = all_rows.clone();
// 3. Iterative execution of recursive member
let mut iteration = 0;
let max_recursion = 100; // Default MS SQL limit
// Hoist table_def clone out of the loop
let table_def_inner = table_def.clone();
while !working_set.is_empty() && iteration < max_recursion {
iteration += 1;
// Temporarily put only the working set into the CTE storage
// so the recursive member sees only the rows from the previous iteration
let mut iteration_ctes = old_ctes.clone();
iteration_ctes.insert(
&cte_def.name,
table_def_inner.clone(),
working_set,
);
let prev_ctes = std::mem::replace(&mut ctx.row.ctes, iteration_ctes);
let step_outcome = self.execute(recursive_stmt.clone(), ctx)?;
ctx.row.ctes = prev_ctes;
let res = match step_outcome {
StmtOutcome::Ok(Some(r)) => r,
StmtOutcome::Ok(None) => break,
// Propagate control flow
other => return other.into_result(),
};
if res.rows.is_empty() {
break;
}
working_set = res
.rows
.iter()
.map(|v| StoredRow {
values: v.clone(),
deleted: false,
})
.collect();
all_rows.extend(working_set.iter().cloned());
}
if iteration >= max_recursion {
return Err(DbError::Execution("The maximum recursion 100 has been exhausted before statement completion.".to_string()));
}
ctx.row.ctes.insert(&cte_def.name, table_def, all_rows);
} else {
return Err(DbError::Execution(
"Recursive CTE must use UNION ALL".into(),
));
}
} else {
return Err(DbError::Execution(
"Recursive CTE must be a UNION ALL of anchor and recursive members".into(),
));
}
} else {
// Standard non-recursive CTE
let cte_outcome = self.execute(cte_def.query.clone(), ctx)?;
let result = match cte_outcome {
StmtOutcome::Ok(Some(r)) => r,
StmtOutcome::Ok(None) => {
return Err(DbError::Execution(
"CTE query must return a result set".into(),
))
}
// Propagate control flow
other => return other.into_result(),
};
let table_def = TableDef {
id: 0,
schema_id: 1,
schema_name: "dbo".to_string(),
name: cte_def.name.clone(),
columns: result
.columns
.iter()
.enumerate()
.map(|(i, name)| crate::catalog::ColumnDef {
id: (i + 1) as u32,
name: name.clone(),
data_type: result.column_types[i].clone(),
nullable: true,
primary_key: false,
unique: false,
identity: None,
default: None,
default_constraint_name: None,
computed_expr: None,
check: None,
check_constraint_name: None,
ansi_padding_on: true,
})
.collect(),
check_constraints: vec![],
foreign_keys: vec![],
};
let rows: Vec<StoredRow> = result
.rows
.into_iter()
.map(|values| StoredRow {
values,
deleted: false,
})
.collect();
ctx.row.ctes.insert(&cte_def.name, table_def, rows);
}
}
let res = self.execute(*stmt.body, ctx);
ctx.row.ctes = old_ctes;
// Propagate control flow from the body; unwrap Ok values
res.map(|outcome| outcome.into_result()).and_then(|r| r)
}
}