PostgreSQL源码学习插入数据#3

  • Z时代
  • 2024-01-10
  • 分类：综合

database

本节介绍heapam_tuple_insert函数的代码流程

相关数据结构

结构体中有些成员可能目前难以理解，暂时先列出来，先把当前用到的成员能搞明白就可以。

// src/include/executor/tuptable.h
typedef struct TupleTableSlot
{
	NodeTag		type;
#define FIELDNO_TUPLETABLESLOT_FLAGS 1
	uint16		tts_flags;		/* Boolean states */
#define FIELDNO_TUPLETABLESLOT_NVALID 2
	AttrNumber	tts_nvalid;		/* # of valid values in tts_values */
	const TupleTableSlotOps *const tts_ops; /* implementation of slot */
#define FIELDNO_TUPLETABLESLOT_TUPLEDESCRIPTOR 4
	TupleDesc	tts_tupleDescriptor;	/* slot"s tuple descriptor */
#define FIELDNO_TUPLETABLESLOT_VALUES 5
	Datum	   *tts_values;		/* current per-attribute values */
#define FIELDNO_TUPLETABLESLOT_ISNULL 6
	bool	   *tts_isnull;		/* current per-attribute isnull flags */
	MemoryContext tts_mcxt;		/* slot itself is in this context */
	ItemPointerData tts_tid;	/* stored tuple"s tid */
	Oid			tts_tableOid;	/* table oid of tuple */
} TupleTableSlot;

static void
heapam_tuple_insert(Relation relation, TupleTableSlot *slot, CommandId cid,
					int options, BulkInsertState bistate);

heapam_tuple_insert函数

/* 获取tuple。在当前示例中其tts_ops指向的是TTSOpsBufferHeapTuple，
   所以调用tts_buffer_heap_get_heap_tuple来取得tuple */
HeapTuple	tuple = ExecFetchSlotHeapTuple(slot, true, &shouldFree);
/* 设置tuple的tableoid为目标relation的oid */
slot->tts_tableOid = RelationGetRelid(relation);
tuple->t_tableOid = slot->tts_tableOid;
/*  插入tuple，复制Item指针到slot->tts_tid */
heap_insert(relation, tuple, cid, options, bistate);
ItemPointerCopy(&tuple->t_self, &slot->tts_tid);
/* 在获取tuple时如果使用了copy，那么现在可以释放了 */
if (shouldFree)
	pfree(tuple);

以上是 PostgreSQL源码学习插入数据#3 的全部内容， 来源链接： utcz.com/z/533154.html

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