postgres源码解析41 btree索引文件的创建--1

在PostgreSQL中，B-tree索引文件的创建是一个复杂的过程，涉及到多个源代码文件。以下是创建B-tree索引的核心函数的简化版本，它展示了如何开始这个过程：

#include "postgres.h"
#include "access/genam.h"
#include "access/btree.h"
#include "access/tableam.h"
#include "catalog/index.h"
#include "catalog/pg_am.h"
#include "commands/tablecmds.h"
#include "storage/smgr.h"
 
/*
 * create_index() -- create an index
 *
 * heapRelation: table to build index on (should be locked by caller)
 * indexRelationName: name of index to create
 * indexOnExpr: expression to index (must be immutable)
 * accessMethodObjectId: OID of index AM to use
 * tableSpaceId: OID of tablespace to use
 * indexUnique: index will enforce unique values
 * indexInfo: other options
 * isPrimary: index is for primary key
 * isUnique: index will be used for unique constraints
 * concurrent: if true, do not lock the table
 *
 * Returns the OID of the created index.
 */
Oid
create_index(Relation heapRelation,
             const char *indexRelationName,
             IndexInfo *indexInfo,
             Oid accessMethodObjectId,
             Oid tableSpaceId,
             bool indexUnique,
             bool isPrimary,
             bool isUnique,
             bool concurrent)
{
    Oid            indexId;
    Relation    indexRelation;
 
    /* ... */
 
    // 创建索引关系
    indexRelation = index_create(heapRelation->rd_rel->relnamespace,
                                 indexRelationName,
                                 indexOnExpr->opno,
                                 indexOnExpr->opclasses,
                                 accessMethodObjectId,
                                 tableSpaceId,
                                 indexUnique,
                                 false, /* is_primary */
                                 concurrent,
                                 indexInfo);
 
    // 设置索引的oid
    indexId = RelationGetRelid(indexRelation);
 
    // ... 其他创建索引的步骤
 
    return indexId;
}

这个简化的代码示例展示了如何在PostgreSQL中创建一个索引关系。实际的创建过程还涉及许多其他的步骤，比如索引页的填充、索引的维护等。这个简化的代码片段旨在展示如何调用相关的API函数来创建一个索引，而不包含具体的实现细节。