mirror of
https://github.com/aljazceru/turso.git
synced 2025-12-29 14:04:22 +01:00
82491ceb6a
This change connects virtual tables with the query optimizer. The optimizer now considers virtual tables during join order search and invokes their best_index callbacks to determine feasible access paths. Currently, this is not a visible change, since none of the existing extensions return information indicating that a plan is invalid.
377 lines
13 KiB
Rust
377 lines
13 KiB
Rust
use std::collections::HashMap;
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use std::sync::Arc;
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use crate::schema::{BTreeTable, Column, Type};
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use crate::translate::optimizer::optimize_select_plan;
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use crate::translate::plan::{Operation, QueryDestination, Scan, Search, SelectPlan};
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use crate::vdbe::builder::CursorType;
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use crate::{
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bail_parse_error,
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schema::{Schema, Table},
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util::normalize_ident,
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vdbe::builder::{ProgramBuilder, ProgramBuilderOpts},
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SymbolTable,
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};
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use turso_sqlite3_parser::ast::{Expr, SortOrder, Update};
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use super::emitter::emit_program;
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use super::expr::process_returning_clause;
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use super::optimizer::optimize_plan;
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use super::plan::{
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ColumnUsedMask, IterationDirection, JoinedTable, Plan, ResultSetColumn, TableReferences,
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UpdatePlan,
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};
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use super::planner::bind_column_references;
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use super::planner::{parse_limit, parse_where};
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/*
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* Update is simple. By default we scan the table, and for each row, we check the WHERE
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* clause. If it evaluates to true, we build the new record with the updated value and insert.
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*
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* EXAMPLE:
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*
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sqlite> explain update t set a = 100 where b = 5;
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addr opcode p1 p2 p3 p4 p5 comment
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---- ------------- ---- ---- ---- ------------- -- -------------
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0 Init 0 16 0 0 Start at 16
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1 Null 0 1 2 0 r[1..2]=NULL
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2 Noop 1 0 1 0
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3 OpenWrite 0 2 0 3 0 root=2 iDb=0; t
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4 Rewind 0 15 0 0
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5 Column 0 1 6 0 r[6]= cursor 0 column 1
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6 Ne 7 14 6 BINARY-8 81 if r[6]!=r[7] goto 14
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7 Rowid 0 2 0 0 r[2]= rowid of 0
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8 IsNull 2 15 0 0 if r[2]==NULL goto 15
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9 Integer 100 3 0 0 r[3]=100
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10 Column 0 1 4 0 r[4]= cursor 0 column 1
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11 Column 0 2 5 0 r[5]= cursor 0 column 2
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12 MakeRecord 3 3 1 0 r[1]=mkrec(r[3..5])
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13 Insert 0 1 2 t 7 intkey=r[2] data=r[1]
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14 Next 0 5 0 1
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15 Halt 0 0 0 0
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16 Transaction 0 1 1 0 1 usesStmtJournal=0
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17 Integer 5 7 0 0 r[7]=5
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18 Goto 0 1 0 0
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*/
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pub fn translate_update(
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schema: &Schema,
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body: &mut Update,
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syms: &SymbolTable,
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mut program: ProgramBuilder,
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connection: &Arc<crate::Connection>,
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) -> crate::Result<ProgramBuilder> {
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let mut plan = prepare_update_plan(&mut program, schema, body, connection)?;
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optimize_plan(&mut plan, schema)?;
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// TODO: freestyling these numbers
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let opts = ProgramBuilderOpts {
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num_cursors: 1,
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approx_num_insns: 20,
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approx_num_labels: 4,
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};
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program.extend(&opts);
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emit_program(&mut program, plan, schema, syms, |_| {})?;
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Ok(program)
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}
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pub fn translate_update_with_after(
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schema: &Schema,
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body: &mut Update,
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syms: &SymbolTable,
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mut program: ProgramBuilder,
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connection: &Arc<crate::Connection>,
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after: impl FnOnce(&mut ProgramBuilder),
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) -> crate::Result<ProgramBuilder> {
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let mut plan = prepare_update_plan(&mut program, schema, body, connection)?;
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optimize_plan(&mut plan, schema)?;
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// TODO: freestyling these numbers
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let opts = ProgramBuilderOpts {
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num_cursors: 1,
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approx_num_insns: 20,
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approx_num_labels: 4,
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};
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program.extend(&opts);
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emit_program(&mut program, plan, schema, syms, after)?;
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Ok(program)
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}
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pub fn prepare_update_plan(
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program: &mut ProgramBuilder,
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schema: &Schema,
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body: &mut Update,
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connection: &Arc<crate::Connection>,
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) -> crate::Result<Plan> {
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if body.with.is_some() {
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bail_parse_error!("WITH clause is not supported");
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}
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if body.or_conflict.is_some() {
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bail_parse_error!("ON CONFLICT clause is not supported");
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}
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let table_name = &body.tbl_name.name;
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if schema.table_has_indexes(&table_name.to_string()) && !schema.indexes_enabled() {
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// Let's disable altering a table with indices altogether instead of checking column by
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// column to be extra safe.
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bail_parse_error!(
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"UPDATE table disabled for table with indexes is disabled. Omit the `--experimental-indexes=false` flag to enable this feature."
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);
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}
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let table = match schema.get_table(table_name.as_str()) {
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Some(table) => table,
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None => bail_parse_error!("Parse error: no such table: {}", table_name),
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};
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let iter_dir = body
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.order_by
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.as_ref()
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.and_then(|order_by| {
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order_by.first().and_then(|ob| {
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ob.order.map(|o| match o {
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SortOrder::Asc => IterationDirection::Forwards,
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SortOrder::Desc => IterationDirection::Backwards,
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})
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})
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})
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.unwrap_or(IterationDirection::Forwards);
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let joined_tables = vec![JoinedTable {
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table: match table.as_ref() {
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Table::Virtual(vtab) => Table::Virtual(vtab.clone()),
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Table::BTree(btree_table) => Table::BTree(btree_table.clone()),
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_ => unreachable!(),
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},
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identifier: table_name.as_str().to_string(),
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internal_id: program.table_reference_counter.next(),
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op: build_scan_op(&table, iter_dir),
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join_info: None,
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col_used_mask: ColumnUsedMask::default(),
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database_id: 0,
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}];
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let mut table_references = TableReferences::new(joined_tables, vec![]);
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let column_lookup: HashMap<String, usize> = table
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.columns()
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.iter()
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.enumerate()
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.filter_map(|(i, col)| col.name.as_ref().map(|name| (name.to_lowercase(), i)))
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.collect();
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let mut set_clauses = Vec::with_capacity(body.sets.len());
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// Process each SET assignment and map column names to expressions
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// e.g the statement `SET x = 1, y = 2, z = 3` has 3 set assigments
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for set in &mut body.sets {
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bind_column_references(&mut set.expr, &mut table_references, None, connection)?;
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let values = match &set.expr {
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Expr::Parenthesized(vals) => vals.clone(),
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expr => vec![expr.clone()],
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};
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if set.col_names.len() != values.len() {
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bail_parse_error!(
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"{} columns assigned {} values",
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set.col_names.len(),
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values.len()
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);
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}
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// Map each column to its corresponding expression
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for (col_name, expr) in set.col_names.iter().zip(values.iter()) {
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let ident = normalize_ident(col_name.as_str());
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let col_index = match column_lookup.get(&ident) {
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Some(idx) => idx,
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None => bail_parse_error!("no such column: {}", ident),
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};
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// Update existing entry or add new one
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match set_clauses.iter_mut().find(|(idx, _)| idx == col_index) {
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Some((_, existing_expr)) => *existing_expr = expr.clone(),
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None => set_clauses.push((*col_index, expr.clone())),
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}
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}
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}
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let (result_columns, _table_references) = if let Some(returning) = &mut body.returning {
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process_returning_clause(
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returning,
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&table,
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body.tbl_name.name.as_str(),
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program,
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connection,
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)?
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} else {
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(
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vec![],
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crate::translate::plan::TableReferences::new(vec![], vec![]),
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)
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};
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let order_by = body.order_by.as_ref().map(|order| {
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order
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.iter()
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.map(|o| (o.expr.clone(), o.order.unwrap_or(SortOrder::Asc)))
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.collect()
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});
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// Sqlite determines we should create an ephemeral table if we do not have a FROM clause
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// Difficult to say what items from the plan can be checked for this so currently just checking if a RowId Alias is referenced
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// https://github.com/sqlite/sqlite/blob/master/src/update.c#L395
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// https://github.com/sqlite/sqlite/blob/master/src/update.c#L670
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let columns = table.columns();
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let rowid_alias_used = set_clauses.iter().fold(false, |accum, (idx, _)| {
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accum || columns[*idx].is_rowid_alias
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});
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let (ephemeral_plan, mut where_clause) = if rowid_alias_used {
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let mut where_clause = vec![];
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let internal_id = program.table_reference_counter.next();
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let joined_tables = vec![JoinedTable {
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table: match table.as_ref() {
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Table::Virtual(vtab) => Table::Virtual(vtab.clone()),
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Table::BTree(btree_table) => Table::BTree(btree_table.clone()),
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_ => unreachable!(),
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},
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identifier: table_name.as_str().to_string(),
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internal_id,
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op: build_scan_op(&table, iter_dir),
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join_info: None,
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col_used_mask: ColumnUsedMask::default(),
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database_id: 0,
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}];
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let mut table_references = TableReferences::new(joined_tables, vec![]);
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// Parse the WHERE clause
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parse_where(
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body.where_clause.as_ref().map(|w| *w.clone()),
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&mut table_references,
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Some(&result_columns),
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&mut where_clause,
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connection,
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)?;
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let table = Arc::new(BTreeTable {
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root_page: 0, // Not relevant for ephemeral table definition
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name: "ephemeral_scratch".to_string(),
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has_rowid: true,
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primary_key_columns: vec![],
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columns: vec![Column {
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name: Some("rowid".to_string()),
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ty: Type::Integer,
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ty_str: "INTEGER".to_string(),
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primary_key: true,
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is_rowid_alias: false,
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notnull: true,
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default: None,
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unique: false,
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collation: None,
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hidden: false,
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}],
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is_strict: false,
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unique_sets: None,
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});
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let temp_cursor_id = program.alloc_cursor_id(CursorType::BTreeTable(table.clone()));
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let mut ephemeral_plan = SelectPlan {
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table_references,
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result_columns: vec![ResultSetColumn {
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expr: Expr::RowId {
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database: None,
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table: internal_id,
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},
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alias: None,
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contains_aggregates: false,
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}],
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where_clause, // original WHERE terms from the UPDATE clause
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group_by: None, // N/A
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order_by: None, // N/A
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aggregates: vec![], // N/A
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limit: None, // N/A
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query_destination: QueryDestination::EphemeralTable {
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cursor_id: temp_cursor_id,
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table,
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},
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join_order: vec![],
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offset: None,
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contains_constant_false_condition: false,
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distinctness: super::plan::Distinctness::NonDistinct,
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values: vec![],
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};
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optimize_select_plan(&mut ephemeral_plan, schema)?;
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let table = ephemeral_plan
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.table_references
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.joined_tables()
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.first()
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.unwrap();
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// We do not need to emit an ephemeral plan if we are not going to loop over the table values
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if matches!(table.op, Operation::Search(Search::RowidEq { .. })) {
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(None, vec![])
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} else {
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(Some(ephemeral_plan), vec![])
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}
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} else {
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(None, vec![])
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};
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if ephemeral_plan.is_none() {
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// Parse the WHERE clause
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parse_where(
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body.where_clause.as_ref().map(|w| *w.clone()),
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&mut table_references,
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Some(&result_columns),
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&mut where_clause,
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connection,
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)?;
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};
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// Parse the LIMIT/OFFSET clause
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let (limit, offset) = body
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.limit
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.as_ref()
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.map(|l| parse_limit(l))
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.unwrap_or(Ok((None, None)))?;
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// Check what indexes will need to be updated by checking set_clauses and see
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// if a column is contained in an index.
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let indexes = schema.get_indices(table_name.as_str());
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let indexes_to_update = indexes
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.iter()
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.filter(|index| {
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index.columns.iter().any(|index_column| {
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set_clauses
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.iter()
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.any(|(set_index_column, _)| index_column.pos_in_table == *set_index_column)
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})
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})
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.cloned()
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.collect();
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Ok(Plan::Update(UpdatePlan {
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table_references,
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set_clauses,
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where_clause,
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returning: if result_columns.is_empty() {
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None
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} else {
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Some(result_columns)
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},
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order_by,
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limit,
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offset,
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contains_constant_false_condition: false,
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indexes_to_update,
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ephemeral_plan,
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}))
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}
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fn build_scan_op(table: &Table, iter_dir: IterationDirection) -> Operation {
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match table {
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Table::BTree(_) => Operation::Scan(Scan::BTreeTable {
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iter_dir,
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index: None,
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}),
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Table::Virtual(_) => Operation::default_scan_for(table),
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_ => unreachable!(),
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}
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}
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