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use std::fmt::Debug;
use anyhow::{anyhow, Result};
use crate::{
ast::{Column, Expr},
eval::Context,
kv::{Range, RangeEnd, RangeIterKV},
Db,
};
#[derive(Debug)]
pub struct RangeScan {
table: String,
alias: String,
tx_id: u64,
index: Option<String>,
range: Range<Expr>,
iter: Option<RangeIterKV>,
}
impl RangeScan {
pub fn new(
table: String,
alias: String,
tx_id: u64,
index: Option<String>,
range: Range<Expr>,
) -> Self {
Self {
range,
iter: None,
table,
alias,
index,
tx_id,
}
}
pub fn execute<'a>(&'a mut self, db: &'a mut Db, mut ctx: Context) -> Result<Option<Context>> {
self.iter = Some(
self.iter
.take()
.map(|x| -> Result<_> { Ok(x) })
.unwrap_or_else(|| {
Ok(RangeIterKV::new(
Range {
backwards: false,
prefix: self
.range
.prefix
.iter()
.map(|e| ctx.eval(e))
.collect::<Result<Vec<_>, _>>()?,
start: self
.range
.start
.as_ref()
.map(|s| -> Result<_> {
Ok(RangeEnd {
inclusive: s.inclusive,
value: ctx.eval(&s.value)?,
})
})
.transpose()?,
end: self
.range
.end
.as_ref()
.map(|e| -> Result<_> {
Ok(RangeEnd {
inclusive: e.inclusive,
value: ctx.eval(&e.value)?,
})
})
.transpose()?,
},
self.tx_id,
self.index.clone().unwrap_or(self.table.clone()),
))
})?,
);
let schema = db.get_table_schema(self.tx_id, &self.table)?;
Ok(self
.iter
.as_mut()
.unwrap()
.next(db)?
.map(|(k, v)| -> Result<_> {
Ok(if self.index.is_some() {
RangeIterKV::new(
Range {
backwards: false,
prefix: v[v.len() - schema.primary_key.len()..].to_vec(),
start: None,
end: None,
},
self.tx_id,
self.table.clone(),
)
.next(db)?
.ok_or(anyhow!("missing table entry for index"))?
} else {
(k, v)
})
})
.transpose()?
.map(|(_, v)| {
for (col, v) in schema.columns.into_iter().zip(v.into_iter()) {
ctx.set(Column(self.alias.clone(), col.name), v);
}
ctx
})
.or_else(|| {
self.iter = None;
None
}))
}
}