feat(minato): support left join in two-table joins (#89)

packages/core/src/database.ts

@@ -244,12 +244,16 @@ export class Database<S = {}, N = {}, C extends Context = Context> extends Servi
     if (Array.isArray(oldTables)) {
       tables = Object.fromEntries(oldTables.map((name) => [name, this.select(name)]))
     }
-    const sels = mapValues(tables, (t: TableLike<S>) => {
+    let sels = mapValues(tables, (t: TableLike<S>) => {
       return typeof t === 'string' ? this.select(t) : t
     })
     if (Object.keys(sels).length === 0) throw new Error('no tables to join')
     const drivers = new Set(Object.values(sels).map(sel => sel.driver))
     if (drivers.size !== 1) throw new Error('cannot join tables from different drivers')
+    if (Object.keys(sels).length === 2 && (optional?.[0] || optional?.[Object.keys(sels)[0]])) {
+      if (optional[1] || optional[Object.keys(sels)[1]]) throw new Error('full join is not supported')
+      sels = Object.fromEntries(Object.entries(sels).reverse())
+    }
     const sel = new Selection([...drivers][0], sels)
     if (Array.isArray(oldTables)) {
       sel.args[0].having = Eval.and(query(...oldTables.map(name => sel.row[name])))

packages/memory/src/index.ts

@@ -32,7 +32,7 @@ export class MemoryDriver extends Driver<MemoryDriver.Config> {
     }
 
     const { ref, query, table, args, model } = sel
-    const { fields, group, having } = sel.args[0]
+    const { fields, group, having, optional = {} } = sel.args[0]
 
     let data: any[]
 
@@ -42,9 +42,15 @@ export class MemoryDriver extends Driver<MemoryDriver.Config> {
         if (!entries.length) return []
         const [[name, rows], ...tail] = entries
         if (!tail.length) return rows.map(row => ({ [name]: row }))
-        return rows.flatMap(row => catesian(tail).map(tail => ({ ...tail, [name]: row })))
+        return rows.flatMap(row => {
+          let res = catesian(tail).map(tail => ({ ...tail, [name]: row }))
+          if (Object.keys(table).length === tail.length + 1) {
+            res = res.map(row => ({ ...env, [ref]: row })).filter(data => executeEval(data, having)).map(x => x[ref])
+          }
+          return !optional[tail[0]?.[0]] || res.length ? res : [{ [name]: row }]
+        })
       }
-      data = catesian(entries).map(x => ({ ...env, [ref]: x })).filter(data => executeEval(data, having)).map(x => x[ref])
+      data = catesian(entries)
     } else {
       data = this.table(table, env).filter(row => executeQuery(row, query, ref, env))
     }

packages/mongo/src/builder.ts

@@ -90,6 +90,7 @@ export class Builder {
   public evalKey?: string
   private refTables: string[] = []
   private refVirtualKeys: Dict<string> = {}
+  private joinTables: Dict<string> = {}
   public aggrDefault: any
 
   private evalOperators: EvalOperators
@@ -102,6 +103,12 @@ export class Builder {
         if (typeof arg === 'string') {
           this.walkedKeys.push(this.getActualKey(arg))
           return this.recursivePrefix + this.getActualKey(arg)
+        }
+        const [joinRoot, ...rest] = (arg[1] as string).split('.')
+        if (this.tables.includes(`${arg[0]}.${joinRoot}`)) {
+          return this.recursivePrefix + rest.join('.')
+        } else if (`${arg[0]}.${joinRoot}` in this.joinTables) {
+          return `$$${this.joinTables[`${arg[0]}.${joinRoot}`]}.` + rest.join('.')
         } else if (this.tables.includes(arg[0])) {
           this.walkedKeys.push(this.getActualKey(arg[1]))
           return this.recursivePrefix + this.getActualKey(arg[1])
@@ -376,6 +383,7 @@ export class Builder {
   protected createSubquery(sel: Selection.Immutable) {
     const predecessor = new Builder(this.driver, Object.keys(sel.tables))
     predecessor.refTables = [...this.refTables, ...this.tables]
+    predecessor.joinTables = { ...this.joinTables }
     predecessor.refVirtualKeys = this.refVirtualKeys
     return predecessor.select(sel)
   }
@@ -391,30 +399,44 @@ export class Builder {
       this.table = predecessor.table
       this.pipeline.push(...predecessor.flushLookups(), ...predecessor.pipeline)
     } else {
-      for (const [name, subtable] of Object.entries(table)) {
+      const refs: Dict<string> = {}
+      Object.entries(table).forEach(([name, subtable], i) => {
         const predecessor = this.createSubquery(subtable)
         if (!predecessor) return
         if (!this.table) {
           this.table = predecessor.table
           this.pipeline.push(...predecessor.flushLookups(), ...predecessor.pipeline, {
             $replaceRoot: { newRoot: { [name]: '$$ROOT' } },
           })
-          continue
+          refs[name] = subtable.ref
+          return
+        }
+        if (sel.args[0].having['$and'].length && i === Object.keys(table).length - 1) {
+          const thisTables = this.tables, thisJoinedTables = this.joinTables
+          this.tables = [...this.tables, `${sel.ref}.${name}`]
+          this.joinTables = {
+            ...this.joinTables,
+            [`${sel.ref}.${name}`]: sel.ref,
+            ...Object.fromEntries(Object.entries(refs).map(([name, ref]) => [`${sel.ref}.${name}`, ref])),
+          }
+          const $expr = this.eval(sel.args[0].having['$and'][0])
+          predecessor.pipeline.push(...this.flushLookups(), { $match: { $expr } })
+          this.tables = thisTables
+          this.joinTables = thisJoinedTables
         }
         const $lookup = {
           from: predecessor.table,
           as: name,
+          let: Object.fromEntries(Object.entries(refs).map(([name, ref]) => [ref, `$$ROOT.${name}`])),
           pipeline: predecessor.pipeline,
         }
         const $unwind = {
           path: `$${name}`,
+          preserveNullAndEmptyArrays: !!sel.args[0].optional?.[name],
         }
         this.pipeline.push({ $lookup }, { $unwind })
-      }
-      if (sel.args[0].having['$and'].length) {
-        const $expr = this.eval(sel.args[0].having)
-        this.pipeline.push(...this.flushLookups(), { $match: { $expr } })
-      }
+        refs[name] = subtable.ref
+      })
     }
 
     // where

packages/sql-utils/src/index.ts

@@ -483,15 +483,21 @@ export class Builder {
       if (!prefix) return
     } else {
       this.state.innerTables = Object.fromEntries(Object.values(table).map(t => [t.ref, t.model]))
-      const joins: string[] = Object.entries(table).map(([key, table]) => {
+      const joins: [string, string][] = Object.entries(table).map(([key, table]) => {
         const restore = this.saveState({ tables: { ...table.tables } })
         const t = `${this.get(table, true, false, false)} AS ${this.escapeId(table.ref)}`
         restore()
-        return t
+        return [key, t]
       })
 
-      // the leading space is to prevent from being parsed as bracketed and added ref
-      prefix = ' ' + joins[0] + joins.slice(1, -1).map(join => ` JOIN ${join} ON ${this.$true}`).join(' ') + ` JOIN ` + joins.at(-1)
+      prefix = [
+        // the leading space is to prevent from being parsed as bracketed and added ref
+        ' ',
+        joins[0][1],
+        ...joins.slice(1, -1).map(([key, join]) => `${args[0].optional?.[key] ? 'LEFT' : ''} JOIN ${join} ON ${this.$true}`),
+        `${args[0].optional?.[joins.at(-1)![0]] ? 'LEFT ' : ''}JOIN`,
+        joins.at(-1)![1],
+      ].join(' ')
       const filter = this.parseEval(args[0].having)
       prefix += ` ON ${filter}`
     }

packages/tests/src/selection.ts

@@ -287,6 +287,42 @@ namespace SelectionTests {
       ).to.eventually.have.length(2)
     })
 
+    it('left join', async () => {
+      await expect(database
+        .join(['foo', 'bar'], (foo, bar) => $.eq(foo.value, bar.value), [false, true])
+        .execute()
+      ).to.eventually.have.shape([
+        {
+          foo: { value: 0, id: 1 },
+          bar: { uid: 1, pid: 1, value: 0, id: 1 },
+        },
+        {
+          foo: { value: 0, id: 1 },
+          bar: { uid: 1, pid: 2, value: 0, id: 3 },
+        },
+        { foo: { value: 2, id: 2 }, bar: {} },
+        { foo: { value: 2, id: 3 }, bar: {} },
+      ])
+
+      await expect(database
+        .join(['foo', 'bar'], (foo, bar) => $.eq(foo.value, bar.value), [true, false])
+        .execute()
+      ).to.eventually.have.shape([
+        {
+          bar: { uid: 1, pid: 1, value: 0, id: 1 },
+          foo: { value: 0, id: 1 },
+        },
+        { bar: { uid: 1, pid: 1, value: 1, id: 2 }, foo: {} },
+        {
+          bar: { uid: 1, pid: 2, value: 0, id: 3 },
+          foo: { value: 0, id: 1 },
+        },
+        { bar: { uid: 1, pid: 3, value: 1, id: 4 }, foo: {} },
+        { bar: { uid: 2, pid: 1, value: 1, id: 5 }, foo: {} },
+        { bar: { uid: 2, pid: 1, value: 1, id: 6 }, foo: {} },
+      ])
+    })
+
     it('group', async () => {
       await expect(database.join(['foo', 'bar'], (foo, bar) => $.eq(foo.id, bar.pid))
         .groupBy('foo', { count: row => $.sum(row.bar.uid) })
@@ -323,9 +359,9 @@ namespace SelectionTests {
           t1: database.select('bar').where(row => $.gt(row.pid, 1)),
           t2: database.select('bar').where(row => $.gt(row.uid, 1)),
           t3: database.select('bar').where(row => $.gt(row.id, 4)),
-        }, ({ t1, t2, t3 }) => $.gt($.add(t1.id, t2.id, t3.id), 0))
+        }, ({ t1, t2, t3 }) => $.gt($.add(t1.id, t2.id, t3.id), 14))
         .execute()
-      ).to.eventually.have.length(8)
+      ).to.eventually.have.length(4)
     })
 
     it('aggregate', async () => {
@@ -442,6 +478,21 @@ namespace SelectionTests {
       ).to.eventually.have.length(6)
     })
 
+    it('selections', async () => {
+      const w = x => database.join(['bar', 'foo']).evaluate(row => $.add($.count(row.bar.id), -6, x))
+      await expect(database
+        .join({
+          t1: database.select('bar').where(row => $.gt(w(row.pid), 1)),
+          t2: database.select('bar').where(row => $.gt(row.uid, 1)),
+          t3: database.select('bar').where(row => $.gt(row.id, w(4))),
+        }, ({ t1, t2, t3 }) => $.gt($.add(t1.id, t2.id, w(t3.id)), 14))
+        .project({
+          val: row => $.add(row.t1.id, row.t2.id, w(row.t3.id)),
+        })
+        .execute()
+      ).to.eventually.have.length(4)
+    })
+
     it('access from join', async () => {
       const w = x => database.select('bar').evaluate(row => $.add($.count(row.id), -6, x))
       await expect(database