pg-native: read all the values of a result in one call when libpq has getvalues

Author: nigrosimone

packages/pg-native/lib/build-result.js

@@ -39,28 +39,34 @@ class Result {
   consumeRows(pq) {
     const tupleCount = pq.ntuples()
     this.rows = new Array(tupleCount)
+    // all the values in one native call when libpq has it, instead of one or two calls per value
+    const values = typeof pq.getvalues === 'function' ? pq.getvalues() : undefined
     for (let i = 0; i < tupleCount; i++) {
-      this.rows[i] = this._arrayMode ? this.consumeRowAsArray(pq, i) : this.consumeRowAsObject(pq, i)
+      this.rows[i] = this._arrayMode ? this.consumeRowAsArray(pq, i, values) : this.consumeRowAsObject(pq, i, values)
     }
   }
 
-  consumeRowAsObject(pq, rowIndex) {
+  consumeRowAsObject(pq, rowIndex, values) {
     const row = { ...this._prebuiltEmptyResultObject }
     for (let j = 0; j < this.fields.length; j++) {
-      row[this.fields[j].name] = this.readValue(pq, rowIndex, j)
+      row[this.fields[j].name] = this.readValue(pq, rowIndex, j, values)
     }
     return row
   }
 
-  consumeRowAsArray(pq, rowIndex) {
+  consumeRowAsArray(pq, rowIndex, values) {
     const row = new Array(this.fields.length)
     for (let j = 0; j < this.fields.length; j++) {
-      row[j] = this.readValue(pq, rowIndex, j)
+      row[j] = this.readValue(pq, rowIndex, j, values)
     }
     return row
   }
 
-  readValue(pq, rowIndex, colIndex) {
+  readValue(pq, rowIndex, colIndex, values) {
+    if (values !== undefined) {
+      const value = values[rowIndex * this.fields.length + colIndex]
+      return value === null ? null : this._parsers[colIndex](value)
+    }
     const rawValue = pq.getvalue(rowIndex, colIndex)
     if (rawValue === '' && pq.getisnull(rowIndex, colIndex)) {
       return null

packages/pg-native/test/build-result.js

@@ -0,0 +1,52 @@
+const assert = require('assert')
+const types = require('pg-types')
+const buildResult = require('../lib/build-result')
+
+// the rows ('brian', 30) and ('', NULL) as libpq returns them
+function fakeResult() {
+  const values = [
+    ['brian', '30'],
+    ['', null],
+  ]
+  return {
+    cmdStatus: () => 'SELECT 2',
+    cmdTuples: () => '2',
+    ntuples: () => values.length,
+    nfields: () => 2,
+    fname: (col) => ['name', 'age'][col],
+    ftype: (col) => [25, 23][col],
+    getvalue: (row, col) => values[row][col] ?? '',
+    getisnull: (row, col) => values[row][col] === null,
+    getvalues: () => values.flat(),
+  }
+}
+
+describe('build result', function () {
+  it('reads all the values in one call when libpq has getvalues', function () {
+    const pq = fakeResult()
+    pq.getvalue = pq.getisnull = () => {
+      throw new Error('one native call per value')
+    }
+    assert.deepStrictEqual(buildResult(pq, types, false).rows, [
+      { name: 'brian', age: 30 },
+      { name: '', age: null },
+    ])
+    assert.deepStrictEqual(buildResult(pq, types, true).rows, [
+      ['brian', 30],
+      ['', null],
+    ])
+  })
+
+  it('reads one value at a time with an older libpq', function () {
+    const pq = fakeResult()
+    delete pq.getvalues
+    assert.deepStrictEqual(buildResult(pq, types, false).rows, [
+      { name: 'brian', age: 30 },
+      { name: '', age: null },
+    ])
+    assert.deepStrictEqual(buildResult(pq, types, true).rows, [
+      ['brian', 30],
+      ['', null],
+    ])
+  })
+})