From 49371e3eca2165e9a34ac6bc35a823de111b4798 Mon Sep 17 00:00:00 2001
From: KentoNion <mrkentonion@gmail.com>
Date: Mon, 13 Oct 2025 00:07:06 +0300
Subject: [PATCH] added postgreSQL placeholders support

---
 batcher/batcher.go | 62 ++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 54 insertions(+), 8 deletions(-)

diff --git a/batcher/batcher.go b/batcher/batcher.go
index c76faa3..48c3dfd 100644
--- a/batcher/batcher.go
+++ b/batcher/batcher.go
@@ -3,6 +3,7 @@ package batcher
 import (
 	"strings"
 	"errors"
+	"strconv"
 
 	"btchrr/models"
 )
@@ -23,7 +24,7 @@ func NewBatcher(batchSize int) (*Batcher, error) {
 		batchSize:    batchSize,
 		placeholders: make(map[string]struct{}),
 	}
-	for _, ph := range []string{"?", "$", ":", ":"} {
+	for _, ph := range []string{"?", "$", ":"} {
 		b.placeholders[ph] = struct{}{}
 	}
 	return b, nil
@@ -36,7 +37,7 @@ func (b *Batcher) BuildBatches(singleQuery string, items []any) ([]models.Batche
 		return []models.BatchedQuery{}, err
 	}
 
-	batches, err := b.BuildBatchQuery(singleQuery, b.batchSize, batchedItems)
+	batches, err := b.BuildBatchQuery(singleQuery, b.batchSize, batchedItems, len(batchedItems))
 	if err != nil {
 		return []models.BatchedQuery{}, err
 	}
@@ -71,7 +72,7 @@ func (b *Batcher) batchItems(items []any) ([][]any, error) {
 }
 
 // BuildBatchQuery - builds a batch query from a single query
-func (b *Batcher) BuildBatchQuery(singleQuery string, batchSize int, batchedItems [][]any) (batchedQueries []models.BatchedQuery, err error) {
+func (b *Batcher) BuildBatchQuery(singleQuery string, batchSize int, batchedItems [][]any, numOfBatches int) (batchedQueries []models.BatchedQuery, err error) {
 	placeholder, err := b.detectPlaceholders(singleQuery)
 	if err != nil {
 		return []models.BatchedQuery{}, err
@@ -79,9 +80,23 @@ func (b *Batcher) BuildBatchQuery(singleQuery string, batchSize int, batchedItem
 
 	switch placeholder {
 	case "?":
-		return b.buildSqliteQuery(singleQuery, batchedItems)
+		for i :=0; i < numOfBatches; i++ {
+			batchQuery, err := b.buildSqliteQuery(singleQuery, batchedItems[i])
+			if err != nil {
+				return []models.BatchedQuery{}, err
+			}
+			batchedQueries = append(batchedQueries, batchQuery)
+		}
+		return
 	case "$":
-		return b.buildPostgresQuery(singleQuery, batchedItems)
+		for i :=0; i < numOfBatches; i++ {
+			batchQuery, err := b.buildPostgresQuery(singleQuery, batchedItems[i])
+			if err != nil {
+				return []models.BatchedQuery{}, err
+			}
+			batchedQueries = append(batchedQueries, batchQuery)
+		}
+		return
 	default:
 		return b.buildQueryWithNamedPlaceholders(singleQuery, placeholder, batchedItems)
 	}
@@ -97,7 +112,7 @@ func (b *Batcher) detectPlaceholders(query string) (string, error) {
 	return "", models.ErrCannotDetectPlaceholder
 }
 
-func (b *Batcher) buildSqliteQuery(singleQuery string, batchedItems [][]any) (batchedQueries models.BatchedQuery, err error) {
+func (b *Batcher) buildSqliteQuery(singleQuery string, batchedItems []any) (batchedQueries models.BatchedQuery, err error) {
 	// INSERT INTO users VALUES (?, ?);
 	idx := strings.Index(strings.ToLower(singleQuery), "values")
 	if idx == -1 {
@@ -121,8 +136,39 @@ func (b *Batcher) buildSqliteQuery(singleQuery string, batchedItems [][]any) (ba
 	return models.BatchedQuery(newQuery), nil
 }
 
-func (b *Batcher) buildPostgresQuery(singleQuery string, batchedItems [][]any) (batchedQueries []models.BatchedQuery, err error) {
-	return []models.BatchedQuery{}, errors.New("not implemented")
+func (b *Batcher) buildPostgresQuery(singleQuery string, batchedItems []any) (batchedQueries models.BatchedQuery, err error) {
+	// INSERT INTO users VALUES ($1, $2);
+	idx := strings.Index(strings.ToLower(singleQuery), "values")
+	if idx == -1 {
+		return "", errors.New("no values found in query")
+	}
+
+	prefix := singleQuery[:idx+6] // +6 - values
+	valuesPart := singleQuery[idx+6:]
+
+	numOfInserts := strings.Count(valuesPart, "$")
+	if numOfInserts == 0 {
+		return "", errors.New("no placeholders found in query")
+	}
+
+	//INSERT INTO users VALUES ($1, $2), ($3, $4), ($5, $6);
+	placeholderNum := 1
+	query := ""
+	for i := 0; i < b.batchSize ; i++ {
+		if i > 0 {
+			query += ", "
+		}
+		query += "("
+		for j := 0; j < numOfInserts; j++ {
+			query += "$" + strconv.Itoa(placeholderNum) + ", "
+			placeholderNum++
+		}
+		query += ")"
+	}
+
+	query = prefix + " " + query + ";"
+
+	return models.BatchedQuery(query), nil
 }
 
 func (b *Batcher) buildQueryWithNamedPlaceholders(singleQuery string, placeholder string, batchedItems [][]any) (batchedQueries []models.BatchedQuery, err error) {