# 单字段搜索
posts = db.query(Post).filter(Post.title.ilike(f'%{keyword}%')).all()

# 多字段联合搜索（OR 关系）
from sqlalchemy import or_
posts = db.query(Post).filter(
    or_(
        Post.title.ilike(f'%{keyword}%'),
        Post.summary.ilike(f'%{keyword}%')
    )
).all()

import math
from fastapi import Query

def get_pagination(page: int = 1, size: int = 6):
    """
    计算分页参数
    page：当前页码（从 1 开始）
    size：每页条数
    """
    skip = (page - 1) * size    # 跳过的记录数
    return skip, size

# 使用示例
skip, limit = get_pagination(page=2, size=6)
# skip = 6, limit = 6 → 跳过前 6 条，取第 7-12 条

# 文件路径：routers/posts.py（扩展 index 路由）
from sqlalchemy import or_
from math import ceil
from fastapi import APIRouter, Depends, Request, Query

@router.get("/", name="index")
def index(
    request: Request,
    category: str | None = Query(None),
    q: str | None = Query(None, description="搜索关键词"),
    page: int = Query(1, ge=1, description="页码"),
    size: int = Query(6, ge=1, le=50, description="每页条数"),
    db: Session = Depends(get_db)
):
    """首页：分类筛选 + 关键词搜索 + 分页"""
    posts_query = db.query(Post).order_by(Post.created_at.desc())

    # 分类筛选
    if category:
        posts_query = posts_query.join(Category).filter(Category.slug == category)

    # 关键词搜索
    if q:
        keyword = f'%{q.strip()}%'
        posts_query = posts_query.filter(
            or_(
                Post.title.ilike(keyword),
                Post.summary.ilike(keyword)
            )
        )

    # 分页
    total = posts_query.count()
    total_pages = ceil(total / size)
    skip = (page - 1) * size
    posts = posts_query.offset(skip).limit(size).all()

    return templates.TemplateResponse("index.html", {
        "request": request,
        "posts": posts,
        "categories": db.query(Category).all(),
        "category_slug": category or "",
        "keyword": q or "",
        "page": page,
        "total_pages": total_pages,
        "total": total
    })

<!-- 在 index.html 的文章列表下方追加分页导航 -->
{% if total_pages > 1 %}
<div class="pagination">
    {% if page > 1 %}
    <a href="/?page={{ page - 1 }}&category={{ category_slug }}&q={{ keyword }}">← 上一页</a>
    {% endif %}

    <span class="page-info">第 {{ page }} 页 / 共 {{ total_pages }} 页</span>

    {% if page < total_pages %}
    <a href="/?page={{ page + 1 }}&category={{ category_slug }}&q={{ keyword }}">下一页 →</a>
    {% endif %}
</div>
{% endif %}