# PostgreSQL 9.5 → 9.6 GUC 差异

> PG9.5 与 PG9.6 之间新增、boot 默认值变化和移除的核心配置参数。
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> [!NOTE]
> **Fact。** 实测在档数从 249 变为 263；新增 14、boot 默认值变化 2、移除 0。

## 新增参数 {#added}

| 参数 | 类型 | Context | Boot 默认值 | 分类 |
| --- | --- | --- | --- | --- |
| [`backend_flush_after`](/zh/parameters/backend-flush-after/) | `integer` | `user` | `0 8kB` (0 B (0 × 8kB)) | Resource Usage / Asynchronous Behavior |
| [`bgwriter_flush_after`](/zh/parameters/bgwriter-flush-after/) | `integer` | `sighup` | `64 8kB` (512 KiB (64 × 8kB)) | Resource Usage / Background Writer |
| [`checkpoint_flush_after`](/zh/parameters/checkpoint-flush-after/) | `integer` | `sighup` | `32 8kB` (256 KiB (32 × 8kB)) | Write-Ahead Log / Checkpoints |
| [`force_parallel_mode`](/zh/parameters/force-parallel-mode/) | `enum` | `user` | `off` | Query Tuning / Other Planner Options |
| [`idle_in_transaction_session_timeout`](/zh/parameters/idle-in-transaction-session-timeout/) | `integer` | `user` | `0 ms` | Client Connection Defaults / Statement Behavior |
| [`max_parallel_workers_per_gather`](/zh/parameters/max-parallel-workers-per-gather/) | `integer` | `user` | `0` | Resource Usage / Asynchronous Behavior |
| [`min_parallel_relation_size`](/zh/parameters/min-parallel-relation-size/) | `integer` | `user` | `1024 8kB` (8 MiB (1024 × 8kB)) | Query Tuning / Planner Cost Constants |
| [`old_snapshot_threshold`](/zh/parameters/old-snapshot-threshold/) | `integer` | `postmaster` | `-1 min` | Resource Usage / Asynchronous Behavior |
| [`parallel_setup_cost`](/zh/parameters/parallel-setup-cost/) | `real` | `user` | `1000` | Query Tuning / Planner Cost Constants |
| [`parallel_tuple_cost`](/zh/parameters/parallel-tuple-cost/) | `real` | `user` | `0.1` | Query Tuning / Planner Cost Constants |
| [`replacement_sort_tuples`](/zh/parameters/replacement-sort-tuples/) | `integer` | `user` | `150000` | Resource Usage / Memory |
| [`syslog_sequence_numbers`](/zh/parameters/syslog-sequence-numbers/) | `bool` | `sighup` | `on` | Reporting and Logging / Where to Log |
| [`syslog_split_messages`](/zh/parameters/syslog-split-messages/) | `bool` | `sighup` | `on` | Reporting and Logging / Where to Log |
| [`wal_writer_flush_after`](/zh/parameters/wal-writer-flush-after/) | `integer` | `sighup` | `128 8kB` (1 MiB (128 × 8kB)) | Write-Ahead Log / Settings |
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## Boot 默认值变化 {#default-changes}

| 参数 | PG9.5 | PG9.6 | 分类 |
| --- | --- | --- | --- |
| [`server_version`](/zh/parameters/server-version/) | `9.5.25` | `9.6.24` | Preset Options |
| [`server_version_num`](/zh/parameters/server-version-num/) | `90525` | `90624` | Preset Options |
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## 移除参数 {#removed}

| 参数 | 最后类型 | Context | 最后 Boot 默认值 | 分类 |
| --- | --- | --- | --- | --- |
| — | — | — | — | — |
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## 计算方法 {#method}

三张清单直接比较固定环境中的 PG9.5 与 PG9.6 `pg_settings` 快照。默认值变化使用 `boot_val` 与 `unit` 的组合；`setting` 不参与判定，以免把 `initdb` 生成值误当作编译时默认值。

- [机器可读差异数据](/data/diffs.json)
- [完整 GUC JSONL](/data/guc.jsonl)