Reuse identical parameters in supported dialects

src/dialect/mssql/mssql-query-compiler.ts

@@ -13,6 +13,16 @@ export class MssqlQueryCompiler extends DefaultQueryCompiler {
     return `@${this.numParameters}`
   }
 
+  protected override getExistingParameterPlaceholder(
+    parameter: unknown,
+  ): string | undefined {
+    const parameterIndex = this.getExistingParameterIndex(parameter)
+    if (parameterIndex === undefined) {
+      return undefined
+    }
+    return `@${parameterIndex + 1}`
+  }
+
   protected override visitOffset(node: OffsetNode): void {
     super.visitOffset(node)
     this.append(' rows')

src/dialect/mysql/mysql-query-compiler.ts

@@ -8,6 +8,10 @@ export class MysqlQueryCompiler extends DefaultQueryCompiler {
     return '?'
   }
 
+  protected override getExistingParameterPlaceholder(_parameter: unknown): undefined {
+    return undefined
+  }
+
   protected override getLeftExplainOptionsWrapper(): string {
     return ''
   }

src/dialect/sqlite/sqlite-query-compiler.ts

@@ -14,6 +14,10 @@ export class SqliteQueryCompiler extends DefaultQueryCompiler {
     return '?'
   }
 
+  protected override getExistingParameterPlaceholder(_parameter: unknown): undefined {
+    return undefined
+  }
+
   protected override getLeftExplainOptionsWrapper(): string {
     return ''
   }

src/query-compiler/default-query-compiler.ts

@@ -1762,8 +1762,12 @@ export class DefaultQueryCompiler
   }
 
   protected appendValue(parameter: unknown): void {
-    this.addParameter(parameter)
-    this.append(this.getCurrentParameterPlaceholder())
+    let parameterPlaceholder = this.getExistingParameterPlaceholder(parameter)
+    if (parameterPlaceholder === undefined) {
+      this.addParameter(parameter)
+      parameterPlaceholder = this.getCurrentParameterPlaceholder()
+    }
+    this.append(parameterPlaceholder)
   }
 
   protected getLeftIdentifierWrapper(): string {
@@ -1774,6 +1778,24 @@ export class DefaultQueryCompiler
     return '"'
   }
 
+  protected getExistingParameterIndex(parameter: unknown): number | undefined {
+    const parameterIndex = this.#parameters.indexOf(parameter)
+    if (parameterIndex < 0) {
+      return undefined
+    }
+    return parameterIndex
+  }
+
+  protected getExistingParameterPlaceholder(
+    parameter: unknown,
+  ): string | undefined {
+    const parameterIndex = this.getExistingParameterIndex(parameter)
+    if (parameterIndex === undefined) {
+      return undefined
+    }
+    return '$' + (parameterIndex + 1)
+  }
+
   protected getCurrentParameterPlaceholder(): string {
     return '$' + this.numParameters
   }

test/node/src/raw-sql.test.ts

@@ -65,6 +65,36 @@ for (const dialect of DIALECTS) {
       await query.execute()
     })
 
+    it('substitutions should reuse identical parameters in supported dialects', async () => {
+      const query = ctx.db
+        .selectFrom('person')
+        .selectAll()
+        .where(
+          sql<boolean>`first_name between ${'A'} and ${'B'} and first_name <> ${'A'}`,
+        )
+
+      testSql(query, dialect, {
+        postgres: {
+          sql: 'select * from "person" where first_name between $1 and $2 and first_name <> $1',
+          parameters: ['A', 'B'],
+        },
+        mysql: {
+          sql: 'select * from `person` where first_name between ? and ? and first_name <> ?',
+          parameters: ['A', 'B', 'A'],
+        },
+        mssql: {
+          sql: 'select * from "person" where first_name between @1 and @2 and first_name <> @1',
+          parameters: ['A', 'B'],
+        },
+        sqlite: {
+          sql: 'select * from "person" where first_name between ? and ? and first_name <> ?',
+          parameters: ['A', 'B', 'A'],
+        },
+      })
+
+      await query.execute()
+    })
+
     it('substitutions should accept queries', async () => {
       const compiler = new DefaultQueryCompiler()