use a non-cryptographic hash to generate unique statement names

jackc · Oct 8, 2023 · aa55f6e · aa55f6e
1 parent 7fc908a
commit aa55f6e
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Showing 3 changed files with 9 additions and 10 deletions.
diff --git a/conn.go b/conn.go
@@ -2,10 +2,9 @@ package pgx
 
 import (
 	"context"
-	"crypto/sha256"
-	"encoding/hex"
 	"errors"
 	"fmt"
+	"hash/fnv"
 	"strconv"
 	"strings"
 	"time"
@@ -318,8 +317,9 @@ func (c *Conn) Prepare(ctx context.Context, name, sql string) (sd *pgconn.Statem
 
 	var psName, psKey string
 	if name == sql {
-		digest := sha256.Sum256([]byte(sql))
-		psName = "stmt_" + hex.EncodeToString(digest[0:24])
+		h := fnv.New64a()
+		h.Write([]byte(sql))
+		psName = "stmt_" + strconv.FormatUint(h.Sum64(), 10)
 		psKey = sql
 	} else {
 		psName = name

diff --git a/go.sum b/go.sum
@@ -6,8 +6,6 @@ github.com/jackc/pgpassfile v1.0.0 h1:/6Hmqy13Ss2zCq62VdNG8tM1wchn8zjSGOBJ6icpsI
 github.com/jackc/pgpassfile v1.0.0/go.mod h1:CEx0iS5ambNFdcRtxPj5JhEz+xB6uRky5eyVu/W2HEg=
 github.com/jackc/pgservicefile v0.0.0-20221227161230-091c0ba34f0a h1:bbPeKD0xmW/Y25WS6cokEszi5g+S0QxI/d45PkRi7Nk=
 github.com/jackc/pgservicefile v0.0.0-20221227161230-091c0ba34f0a/go.mod h1:5TJZWKEWniPve33vlWYSoGYefn3gLQRzjfDlhSJ9ZKM=
-github.com/jackc/puddle/v2 v2.2.0 h1:RdcDk92EJBuBS55nQMMYFXTxwstHug4jkhT5pq8VxPk=
-github.com/jackc/puddle/v2 v2.2.0/go.mod h1:vriiEXHvEE654aYKXXjOvZM39qJ0q+azkZFrfEOc3H4=
 github.com/jackc/puddle/v2 v2.2.1 h1:RhxXJtFG022u4ibrCSMSiu5aOq1i77R3OHKNJj77OAk=
 github.com/jackc/puddle/v2 v2.2.1/go.mod h1:vriiEXHvEE654aYKXXjOvZM39qJ0q+azkZFrfEOc3H4=
 github.com/kr/pretty v0.1.0/go.mod h1:dAy3ld7l9f0ibDNOQOHHMYYIIbhfbHSm3C4ZsoJORNo=

diff --git a/internal/stmtcache/stmtcache.go b/internal/stmtcache/stmtcache.go
@@ -2,17 +2,18 @@
 package stmtcache
 
 import (
-	"crypto/sha256"
-	"encoding/hex"
+	"hash/fnv"
+	"strconv"
 
 	"github.com/jackc/pgx/v5/pgconn"
 )
 
 // StatementName returns a statement name that will be stable for sql across multiple connections and program
 // executions.
 func StatementName(sql string) string {
-	digest := sha256.Sum256([]byte(sql))
-	return "stmtcache_" + hex.EncodeToString(digest[0:24])
+	h := fnv.New64a()
+	h.Write([]byte(sql))
+	return "stmtcache_" + strconv.FormatUint(h.Sum64(), 10)
 }
 
 // Cache caches statement descriptions.