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Unify SELECT .. LIMIT handling in translate_select()

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Working towards a saner translate_select(), let's unify `SELECT ..
LIMIT` handling across different types of select statements.
This commit is contained in:
Pekka Enberg
2024-06-24 21:36:34 +03:00
parent bdbbbda84f
commit 6290c8167d
1 changed files with 19 additions and 21 deletions
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40
core/translate.rs
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@@ -64,7 +64,13 @@ fn translate_select(schema: &Schema, select: Select) -> Result<Program> {
let mut program = ProgramBuilder::new();
let init_offset = program.emit_placeholder();
let start_offset = program.offset();
match select.body.select {
let limit_reg = if let Some(limit) = select.limit {
assert!(limit.offset.is_none());
Some(translate_expr(&mut program, None, None, &limit.expr))
} else {
None
};
let limit_decr_insn = match select.body.select {
OneSelect::Select {
columns,
from: Some(from),
@@ -84,17 +90,6 @@ fn translate_select(schema: &Schema, select: Select) -> Result<Program> {
None => anyhow::bail!("Parse error: no such table: {}", table_name),
};
let root_page = table.root_page;
let limit_reg = if let Some(limit) = select.limit {
assert!(limit.offset.is_none());
Some(translate_expr(
&mut program,
Some(cursor_id),
Some(table),
&limit.expr,
))
} else {
None
};
program.emit_insn(Insn::OpenReadAsync {
cursor_id,
root_page,
@@ -121,15 +116,7 @@ fn translate_select(schema: &Schema, select: Select) -> Result<Program> {
pc_if_empty: program.offset(),
},
);
if let Some(limit_decr_insn) = limit_decr_insn {
program.fixup_insn(
limit_decr_insn,
Insn::DecrJumpZero {
reg: limit_reg.unwrap(),
target_pc: program.offset(),
},
);
}
limit_decr_insn
}
OneSelect::Select {
columns,
@@ -142,8 +129,19 @@ fn translate_select(schema: &Schema, select: Select) -> Result<Program> {
register_start,
register_end,
});
let limit_decr_insn = limit_reg.map(|_| program.emit_placeholder());
limit_decr_insn
}
_ => todo!(),
};
if let Some(limit_decr_insn) = limit_decr_insn {
program.fixup_insn(
limit_decr_insn,
Insn::DecrJumpZero {
reg: limit_reg.unwrap(),
target_pc: program.offset(),
},
);
}
program.emit_insn(Insn::Halt);
program.fixup_insn(