TsDB2/DB/core/LikeCondition.go

package core

import (
	"strings"
)

type LikeCondition struct {
	Field         string
	Pattern       string
	CaseSensitive bool
}

func Like(field string, pattern string) Condition {
	return LikeCondition{Field: field, Pattern: pattern, CaseSensitive: true}
}

func ILike(field string, pattern string) Condition {
	return LikeCondition{Field: field, Pattern: pattern, CaseSensitive: false}
}

func (c LikeCondition) Fields() []string {
	return []string{c.Field}
}

func (c LikeCondition) Match(row []byte, table *Table) bool {
	fieldIdx := table.findFieldIndex(c.Field)
	if fieldIdx < 0 {
		return false
	}

	offset, ok := table.getVersionedOffset(row, fieldIdx)
	if !ok {
		return false
	}
	fieldInfo := table.Field[fieldIdx]

	// 读取字符串值; 宽度取列声明的宽度 (含字符串宽度码), 否则宽字符串列会被切短
	size := int(fieldInfo.Width())
	if size <= 0 || int(offset)+size > len(row) {
		return false
	}
	stored := strings.TrimRight(string(row[offset:int(offset)+size]), "\x00")

	// 模式匹配
	if !c.CaseSensitive {
		stored = strings.ToLower(stored)
		pattern := strings.ToLower(c.Pattern)
		return likeMatch(stored, pattern)
	}
	return likeMatch(stored, c.Pattern)
}

// likeMatch 简单的 LIKE 模式匹配（支持 % 和 _）
func likeMatch(str, pattern string) bool {
	// 将 LIKE 模式转换为简单的通配符匹配
	// % 匹配任意字符序列（包括空序列）
	// _ 匹配任意单个字符

	// 简化实现：使用 strings.Contains 处理 %
	parts := strings.Split(pattern, "%")

	if len(parts) == 1 {
		// 没有 %，直接比较
		return str == pattern
	}

	// 检查前缀
	if parts[0] != "" && !strings.HasPrefix(str, parts[0]) {
		return false
	}

	// 检查后缀
	if parts[len(parts)-1] != "" && !strings.HasSuffix(str, parts[len(parts)-1]) {
		return false
	}

	// 检查中间部分
	current := str
	if parts[0] != "" {
		current = current[len(parts[0]):]
	}

	for i := 1; i < len(parts); i++ {
		idx := strings.Index(current, parts[i])
		if idx == -1 {
			return false
		}
		current = current[idx+len(parts[i]):]
	}

	return true
}