turso/core/translate.rs

use std::cell::RefCell;
use std::rc::Rc;

use crate::expr::{build_select, maybe_apply_affinity, translate_expr};
use crate::function::{AggFunc, Func};
use crate::pager::Pager;
use crate::schema::{Schema, Table};
use crate::select::{ColumnInfo, LoopInfo, Select, SrcTable};
use crate::sqlite3_ondisk::{DatabaseHeader, MIN_PAGE_CACHE_SIZE};
use crate::vdbe::{BranchOffset, Insn, Program, ProgramBuilder};
use crate::where_clause::{
    evaluate_conditions, translate_conditions, translate_where, Inner, Left, QueryConstraint,
};
use anyhow::Result;
use sqlite3_parser::ast::{self, Literal};

struct LimitInfo {
    limit_reg: usize,
    num: i64,
    goto_label: BranchOffset,
}

/// Translate SQL statement into bytecode program.
pub fn translate(
    schema: &Schema,
    stmt: ast::Stmt,
    database_header: Rc<RefCell<DatabaseHeader>>,
    pager: Rc<Pager>,
) -> Result<Program> {
    match stmt {
        ast::Stmt::Select(select) => {
            let select = build_select(schema, &select)?;
            translate_select(select)
        }
        ast::Stmt::Pragma(name, body) => translate_pragma(&name, body, database_header, pager),
        _ => todo!(),
    }
}

/// Generate code for a SELECT statement.
fn translate_select(mut select: Select) -> Result<Program> {
    let mut program = ProgramBuilder::new();
    let init_label = program.allocate_label();
    program.emit_insn_with_label_dependency(
        Insn::Init {
            target_pc: init_label,
        },
        init_label,
    );
    let start_offset = program.offset();

    let limit_info = if let Some(limit) = &select.limit {
        assert!(limit.offset.is_none());
        let target_register = program.alloc_register();
        let limit_reg = translate_expr(&mut program, &select, &limit.expr, target_register)?;
        let num = if let ast::Expr::Literal(ast::Literal::Numeric(num)) = &limit.expr {
            num.parse::<i64>()?
        } else {
            todo!();
        };
        let goto_label = program.allocate_label();
        if num == 0 {
            program.emit_insn_with_label_dependency(
                Insn::Goto {
                    target_pc: goto_label,
                },
                goto_label,
            );
        }
        Some(LimitInfo {
            limit_reg,
            num,
            goto_label,
        })
    } else {
        None
    };

    if !select.src_tables.is_empty() {
        let constraint = translate_tables_begin(&mut program, &mut select)?;

        let (register_start, register_end) = translate_columns(&mut program, &select)?;

        if !select.exist_aggregation {
            program.emit_insn(Insn::ResultRow {
                start_reg: register_start,
                count: register_end - register_start,
            });
            emit_limit_insn(&limit_info, &mut program);
        }

        translate_tables_end(&mut program, &select, constraint);

        if select.exist_aggregation {
            let mut target = register_start;
            for info in &select.column_info {
                if let Some(Func::Agg(func)) = &info.func {
                    program.emit_insn(Insn::AggFinal {
                        register: target,
                        func: func.clone(),
                    });
                }
                target += info.columns_to_allocate;
            }
            // only one result row
            program.emit_insn(Insn::ResultRow {
                start_reg: register_start,
                count: register_end - register_start,
            });
            emit_limit_insn(&limit_info, &mut program);
        }
    } else {
        assert!(!select.exist_aggregation);
        let where_maybe = translate_where(&select, &mut program)?;
        let (register_start, register_end) = translate_columns(&mut program, &select)?;
        if let Some(where_clause_label) = where_maybe {
            program.resolve_label(where_clause_label, program.offset() + 1);
        }
        program.emit_insn(Insn::ResultRow {
            start_reg: register_start,
            count: register_end - register_start,
        });
        emit_limit_insn(&limit_info, &mut program);
    };
    program.emit_insn(Insn::Halt);
    let halt_offset = program.offset() - 1;
    if let Some(limit_info) = limit_info {
        if limit_info.goto_label < 0 {
            program.resolve_label(limit_info.goto_label, halt_offset);
        }
    }
    program.resolve_label(init_label, program.offset());
    program.emit_insn(Insn::Transaction);
    program.emit_constant_insns();
    program.emit_insn(Insn::Goto {
        target_pc: start_offset,
    });
    program.resolve_deferred_labels();
    Ok(program.build())
}

fn emit_limit_insn(limit_info: &Option<LimitInfo>, program: &mut ProgramBuilder) {
    if limit_info.is_none() {
        return;
    }
    let limit_info = limit_info.as_ref().unwrap();
    if limit_info.num > 0 {
        program.emit_insn_with_label_dependency(
            Insn::DecrJumpZero {
                reg: limit_info.limit_reg,
                target_pc: limit_info.goto_label,
            },
            limit_info.goto_label,
        );
    }
}

fn translate_tables_begin(
    program: &mut ProgramBuilder,
    select: &mut Select,
) -> Result<Option<QueryConstraint>> {
    for join in &select.src_tables {
        let loop_info = translate_table_open_cursor(program, join);
        select.loops.push(loop_info);
    }

    let conditions = evaluate_conditions(program, select)?;

    for loop_info in &mut select.loops {
        let mut left_join_match_flag_maybe = None;
        if let Some(QueryConstraint::Left(Left {
            match_flag,
            right_cursor,
            ..
        })) = conditions.as_ref()
        {
            if loop_info.open_cursor == *right_cursor {
                left_join_match_flag_maybe = Some(*match_flag);
            }
        }
        translate_table_open_loop(program, loop_info, left_join_match_flag_maybe);
    }

    translate_conditions(program, select, conditions)
}

fn handle_skip_row(
    program: &mut ProgramBuilder,
    cursor_id: usize,
    next_row_instruction_offset: BranchOffset,
    constraint: &Option<QueryConstraint>,
) {
    match constraint {
        Some(QueryConstraint::Left(Left {
            where_clause,
            join_clause,
            match_flag,
            match_flag_hit_marker,
            found_match_next_row_label,
            left_cursor,
            right_cursor,
            ..
        })) => {
            if let Some(where_clause) = where_clause {
                if where_clause.no_match_target_cursor == cursor_id {
                    program.resolve_label(
                        where_clause.no_match_jump_label,
                        next_row_instruction_offset,
                    );
                }
            }
            if let Some(join_clause) = join_clause {
                if join_clause.no_match_target_cursor == cursor_id {
                    program.resolve_label(
                        join_clause.no_match_jump_label,
                        next_row_instruction_offset,
                    );
                }
            }
            if cursor_id == *right_cursor {
                // If the left join match flag has been set to 1, we jump to the next row (result row has been emitted already)
                program.emit_insn_with_label_dependency(
                    Insn::IfPos {
                        reg: *match_flag,
                        target_pc: *found_match_next_row_label,
                        decrement_by: 0,
                    },
                    *found_match_next_row_label,
                );
                // If not, we set the right table cursor's "pseudo null bit" on, which means any Insn::Column will return NULL
                program.emit_insn(Insn::NullRow {
                    cursor_id: *right_cursor,
                });
                // Jump to setting the left join match flag to 1 again, but this time the right table cursor will set everything to null
                program.emit_insn_with_label_dependency(
                    Insn::Goto {
                        target_pc: *match_flag_hit_marker,
                    },
                    *match_flag_hit_marker,
                );
            }
            if cursor_id == *left_cursor {
                program.resolve_label(*found_match_next_row_label, next_row_instruction_offset);
            }
        }
        Some(QueryConstraint::Inner(Inner {
            where_clause,
            join_clause,
            ..
        })) => {
            if let Some(join_clause) = join_clause {
                if cursor_id == join_clause.no_match_target_cursor {
                    program.resolve_label(
                        join_clause.no_match_jump_label,
                        next_row_instruction_offset,
                    );
                }
            }
            if let Some(where_clause) = where_clause {
                if cursor_id == where_clause.no_match_target_cursor {
                    program.resolve_label(
                        where_clause.no_match_jump_label,
                        next_row_instruction_offset,
                    );
                }
            }
        }
        None => {}
    }
}

fn translate_tables_end(
    program: &mut ProgramBuilder,
    select: &Select,
    constraint: Option<QueryConstraint>,
) {
    // iterate in reverse order as we open cursors in order
    for table_loop in select.loops.iter().rev() {
        let cursor_id = table_loop.open_cursor;
        let next_row_instruction_offset = program.offset();
        program.emit_insn(Insn::NextAsync { cursor_id });
        program.emit_insn(Insn::NextAwait {
            cursor_id,
            pc_if_next: table_loop.rewind_offset as BranchOffset,
        });
        program.resolve_label(table_loop.rewind_label, program.offset());
        handle_skip_row(program, cursor_id, next_row_instruction_offset, &constraint);
    }
}

fn translate_table_open_cursor(program: &mut ProgramBuilder, table: &SrcTable) -> LoopInfo {
    let table_identifier = match table.alias {
        Some(alias) => alias.clone(),
        None => table.table.get_name().to_string(),
    };
    let cursor_id = program.alloc_cursor_id(table_identifier, table.table.clone());
    let root_page = match &table.table {
        Table::BTree(btree) => btree.root_page,
        Table::Pseudo(_) => todo!(),
    };
    program.emit_insn(Insn::OpenReadAsync {
        cursor_id,
        root_page,
    });
    program.emit_insn(Insn::OpenReadAwait);
    LoopInfo {
        open_cursor: cursor_id,
        rewind_offset: 0,
        rewind_label: 0,
    }
}

fn translate_table_open_loop(
    program: &mut ProgramBuilder,
    loop_info: &mut LoopInfo,
    left_join_match_flag_maybe: Option<usize>,
) {
    if let Some(match_flag) = left_join_match_flag_maybe {
        // Initialize left join as not matched
        program.emit_insn(Insn::Integer {
            value: 0,
            dest: match_flag,
        });
    }
    program.emit_insn(Insn::RewindAsync {
        cursor_id: loop_info.open_cursor,
    });
    let rewind_await_label = program.allocate_label();
    program.emit_insn_with_label_dependency(
        Insn::RewindAwait {
            cursor_id: loop_info.open_cursor,
            pc_if_empty: rewind_await_label,
        },
        rewind_await_label,
    );
    loop_info.rewind_label = rewind_await_label;
    loop_info.rewind_offset = program.offset() - 1;
}

fn translate_columns(program: &mut ProgramBuilder, select: &Select) -> Result<(usize, usize)> {
    let register_start = program.next_free_register();

    // allocate one register as output for each col
    let registers: usize = select
        .column_info
        .iter()
        .map(|col| col.columns_to_allocate)
        .sum();
    program.alloc_registers(registers);
    let register_end = program.next_free_register();

    let mut target = register_start;
    for (col, info) in select.columns.iter().zip(select.column_info.iter()) {
        translate_column(program, select, col, info, target)?;
        target += info.columns_to_allocate;
    }
    Ok((register_start, register_end))
}

fn translate_column(
    program: &mut ProgramBuilder,
    select: &Select,
    col: &ast::ResultColumn,
    info: &ColumnInfo,
    target_register: usize, // where to store the result, in case of star it will be the start of registers added
) -> Result<()> {
    match col {
        ast::ResultColumn::Expr(expr, _) => {
            if info.is_aggregation_function() {
                let _ = translate_aggregation(program, select, expr, info, target_register)?;
            } else {
                let _ = translate_expr(program, select, expr, target_register)?;
            }
        }
        ast::ResultColumn::Star => {
            let mut target_register = target_register;
            for join in &select.src_tables {
                translate_table_star(join, program, target_register);
                target_register += &join.table.columns().len();
            }
        }
        ast::ResultColumn::TableStar(_) => todo!(),
    }
    Ok(())
}

fn translate_table_star(table: &SrcTable, program: &mut ProgramBuilder, target_register: usize) {
    let table_identifier = match table.alias {
        Some(alias) => alias.clone(),
        None => table.table.get_name().to_string(),
    };
    let table_cursor = program.resolve_cursor_id(&table_identifier);
    let table = &table.table;
    for (i, col) in table.columns().iter().enumerate() {
        let col_target_register = target_register + i;
        if table.column_is_rowid_alias(col) {
            program.emit_insn(Insn::RowId {
                cursor_id: table_cursor,
                dest: col_target_register,
            });
        } else {
            program.emit_insn(Insn::Column {
                column: i,
                dest: col_target_register,
                cursor_id: table_cursor,
            });
            maybe_apply_affinity(col, col_target_register, program);
        }
    }
}

fn translate_aggregation(
    program: &mut ProgramBuilder,
    select: &Select,
    expr: &ast::Expr,
    info: &ColumnInfo,
    target_register: usize,
) -> Result<usize> {
    let _ = expr;
    assert!(info.func.is_some());
    let func = info.func.as_ref().unwrap();
    let empty_args = &Vec::<ast::Expr>::new();
    let args = info.args.as_ref().unwrap_or(empty_args);
    let dest = match func {
        Func::SingleRow(_) => anyhow::bail!("Parse error: single row function in aggregation"),
        Func::Agg(agg_func) => match agg_func {
            AggFunc::Avg => {
                if args.len() != 1 {
                    anyhow::bail!("Parse error: avg bad number of arguments");
                }
                let expr = &args[0];
                let expr_reg = program.alloc_register();
                let _ = translate_expr(program, select, expr, expr_reg)?;
                program.emit_insn(Insn::AggStep {
                    acc_reg: target_register,
                    col: expr_reg,
                    delimiter: 0,
                    func: AggFunc::Avg,
                });
                target_register
            }
            AggFunc::Count => {
                let expr_reg = if args.is_empty() {
                    program.alloc_register()
                } else {
                    let expr = &args[0];
                    let expr_reg = program.alloc_register();
                    let _ = translate_expr(program, select, expr, expr_reg);
                    expr_reg
                };
                program.emit_insn(Insn::AggStep {
                    acc_reg: target_register,
                    col: expr_reg,
                    delimiter: 0,
                    func: AggFunc::Count,
                });
                target_register
            }
            AggFunc::GroupConcat => {
                if args.len() != 1 && args.len() != 2 {
                    anyhow::bail!("Parse error: group_concat bad number of arguments");
                }

                let expr_reg = program.alloc_register();
                let delimiter_reg = program.alloc_register();

                let expr = &args[0];
                let delimiter_expr: ast::Expr;

                if args.len() == 2 {
                    match &args[1] {
                        ast::Expr::Id(ident) => {
                            if ident.0.starts_with('"') {
                                delimiter_expr =
                                    ast::Expr::Literal(Literal::String(ident.0.to_string()));
                            } else {
                                delimiter_expr = args[1].clone();
                            }
                        }
                        ast::Expr::Literal(Literal::String(s)) => {
                            delimiter_expr = ast::Expr::Literal(Literal::String(s.to_string()));
                        }
                        _ => anyhow::bail!("Incorrect delimiter parameter"),
                    };
                } else {
                    delimiter_expr = ast::Expr::Literal(Literal::String(String::from("\",\"")));
                }

                if let Err(error) = translate_expr(program, select, expr, expr_reg) {
                    anyhow::bail!(error);
                }
                if let Err(error) = translate_expr(program, select, &delimiter_expr, delimiter_reg)
                {
                    anyhow::bail!(error);
                }

                program.emit_insn(Insn::AggStep {
                    acc_reg: target_register,
                    col: expr_reg,
                    delimiter: delimiter_reg,
                    func: AggFunc::GroupConcat,
                });

                target_register
            }
            AggFunc::Max => {
                if args.len() != 1 {
                    anyhow::bail!("Parse error: max bad number of arguments");
                }
                let expr = &args[0];
                let expr_reg = program.alloc_register();
                let _ = translate_expr(program, select, expr, expr_reg);
                program.emit_insn(Insn::AggStep {
                    acc_reg: target_register,
                    col: expr_reg,
                    delimiter: 0,
                    func: AggFunc::Max,
                });
                target_register
            }
            AggFunc::Min => {
                if args.len() != 1 {
                    anyhow::bail!("Parse error: min bad number of arguments");
                }
                let expr = &args[0];
                let expr_reg = program.alloc_register();
                let _ = translate_expr(program, select, expr, expr_reg);
                program.emit_insn(Insn::AggStep {
                    acc_reg: target_register,
                    col: expr_reg,
                    delimiter: 0,
                    func: AggFunc::Min,
                });
                target_register
            }
            AggFunc::StringAgg => {
                if args.len() != 2 {
                    anyhow::bail!("Parse error: string_agg bad number of arguments");
                }

                let expr_reg = program.alloc_register();
                let delimiter_reg = program.alloc_register();

                let expr = &args[0];
                let delimiter_expr: ast::Expr;

                match &args[1] {
                    ast::Expr::Id(ident) => {
                        if ident.0.starts_with('"') {
                            anyhow::bail!("Parse error: no such column: \",\" - should this be a string literal in single-quotes?");
                        } else {
                            delimiter_expr = args[1].clone();
                        }
                    }
                    ast::Expr::Literal(Literal::String(s)) => {
                        delimiter_expr = ast::Expr::Literal(Literal::String(s.to_string()));
                    }
                    _ => anyhow::bail!("Incorrect delimiter parameter"),
                };

                if let Err(error) = translate_expr(program, select, expr, expr_reg) {
                    anyhow::bail!(error);
                }
                if let Err(error) = translate_expr(program, select, &delimiter_expr, delimiter_reg)
                {
                    anyhow::bail!(error);
                }

                program.emit_insn(Insn::AggStep {
                    acc_reg: target_register,
                    col: expr_reg,
                    delimiter: delimiter_reg,
                    func: AggFunc::StringAgg,
                });

                target_register
            }
            AggFunc::Sum => {
                if args.len() != 1 {
                    anyhow::bail!("Parse error: sum bad number of arguments");
                }
                let expr = &args[0];
                let expr_reg = program.alloc_register();
                let _ = translate_expr(program, select, expr, expr_reg)?;
                program.emit_insn(Insn::AggStep {
                    acc_reg: target_register,
                    col: expr_reg,
                    delimiter: 0,
                    func: AggFunc::Sum,
                });
                target_register
            }
            AggFunc::Total => {
                if args.len() != 1 {
                    anyhow::bail!("Parse error: total bad number of arguments");
                }
                let expr = &args[0];
                let expr_reg = program.alloc_register();
                let _ = translate_expr(program, select, expr, expr_reg)?;
                program.emit_insn(Insn::AggStep {
                    acc_reg: target_register,
                    col: expr_reg,
                    delimiter: 0,
                    func: AggFunc::Total,
                });
                target_register
            }
        },
    };
    Ok(dest)
}

fn translate_pragma(
    name: &ast::QualifiedName,
    body: Option<ast::PragmaBody>,
    database_header: Rc<RefCell<DatabaseHeader>>,
    pager: Rc<Pager>,
) -> Result<Program> {
    let mut program = ProgramBuilder::new();
    let init_label = program.allocate_label();
    program.emit_insn_with_label_dependency(
        Insn::Init {
            target_pc: init_label,
        },
        init_label,
    );
    let start_offset = program.offset();
    match body {
        None => {
            let pragma_result = program.alloc_register();

            program.emit_insn(Insn::Integer {
                value: database_header.borrow().default_cache_size.into(),
                dest: pragma_result,
            });

            let pragma_result_end = program.next_free_register();
            program.emit_insn(Insn::ResultRow {
                start_reg: pragma_result,
                count: pragma_result_end - pragma_result,
            });
        }
        Some(ast::PragmaBody::Equals(value)) => {
            let value_to_update = match value {
                ast::Expr::Literal(ast::Literal::Numeric(numeric_value)) => {
                    numeric_value.parse::<i64>().unwrap()
                }
                ast::Expr::Unary(ast::UnaryOperator::Negative, expr) => match *expr {
                    ast::Expr::Literal(ast::Literal::Numeric(numeric_value)) => {
                        -numeric_value.parse::<i64>().unwrap()
                    }
                    _ => 0,
                },
                _ => 0,
            };
            update_pragma(&name.name.0, value_to_update, database_header, pager);
        }
        Some(ast::PragmaBody::Call(_)) => {
            todo!()
        }
    };
    program.emit_insn(Insn::Halt);
    program.resolve_label(init_label, program.offset());
    program.emit_insn(Insn::Transaction);
    program.emit_constant_insns();
    program.emit_insn(Insn::Goto {
        target_pc: start_offset,
    });
    program.resolve_deferred_labels();
    Ok(program.build())
}

fn update_pragma(name: &str, value: i64, header: Rc<RefCell<DatabaseHeader>>, pager: Rc<Pager>) {
    match name {
        "cache_size" => {
            let mut cache_size_unformatted = value;
            let mut cache_size = if cache_size_unformatted < 0 {
                let kb = cache_size_unformatted.abs() * 1024;
                kb / 512 // assume 512 page size for now
            } else {
                value
            } as usize;
            if cache_size < MIN_PAGE_CACHE_SIZE {
                // update both in memory and stored disk value
                cache_size = MIN_PAGE_CACHE_SIZE;
                cache_size_unformatted = MIN_PAGE_CACHE_SIZE as i64;
            }

            // update in-memory header
            header.borrow_mut().default_cache_size = cache_size_unformatted
                .try_into()
                .unwrap_or_else(|_| panic!("invalid value, too big for a i32 {}", value));

            // update in disk
            let header_copy = header.borrow().clone();
            pager.write_database_header(&header_copy);

            // update cache size
            pager.change_page_cache_size(cache_size);
        }
        _ => todo!(),
    }
}