PostgreSQL数据库事务系统Upper Layer——EndTransactionBlock

PostgreSQL数据库事务系统Upper Layer——EndTransactionBlock

EndTransactionBlock执行一个commit命令。COMMIT命令有可能做的是ROLLBACK操作，EndTransactionBlock函数返回true代表COMMIT，false代表ROLLBACK。在该函数中处理改变事物状态块的状态，其他工作由后续CommitTransactionCommand函数处理。

事务状态由TBLOCK_INPROGRESS改变为TBLOCK_END，标记result为true代表COMMIT事务状态TBLOCK_IMPLICIT_INPROGRESS，如果处于事务链chain，直接报错，否则直接将事务状态改变为TBLOCK_END，标记result为true代表COMMIT

bool EndTransactionBlock(bool chain) { TransactionState s = CurrentTransactionState; bool result = false; switch (s->blockState) { /* We are in a transaction block, so tell CommitTransactionCommand to COMMIT. */ case TBLOCK_INPROGRESS: s->blockState = TBLOCK_END; result = true; break; /* We are in an implicit transaction block. If AND CHAIN was specified, error. Otherwise commit, but issue a warning because there was no explicit BEGIN before this. */ case TBLOCK_IMPLICIT_INPROGRESS: if (chain) ereport(ERROR, (errcode(ERRCODE_NO_ACTIVE_SQL_TRANSACTION),/* translator: %s represents an SQL statement name */ errmsg("%s can only be used in transaction blocks","COMMIT AND CHAIN"))); else ereport(WARNING, (errcode(ERRCODE_NO_ACTIVE_SQL_TRANSACTION), errmsg("there is no transaction in progress"))); s->blockState = TBLOCK_END; result = true; break;

事务状态由TBLOCK_ABORT改变为TBLOCK_ABORT_END，标记result为fasle代表ROLLBACK

/* We are in a failed transaction block. Tell CommitTransactionCommand it's time to exit the block. */ case TBLOCK_ABORT: s->blockState = TBLOCK_ABORT_END; break;

事务状态处于TBLOCK_SUBINPROGRESS子事务中，将子事务状态改为TBLOCK_SUBCOMMIT，循环处理父事务。最后处理顶层事务将事务状态由TBLOCK_INPROGRESS转变为TBLOCK_END，标记result为true代表COMMIT

/* We are in a live subtransaction block. Set up to subcommit all open subtransactions and then commit the main transaction. */ case TBLOCK_SUBINPROGRESS: while (s->parent != NULL) { if (s->blockState == TBLOCK_SUBINPROGRESS) s->blockState = TBLOCK_SUBCOMMIT; else elog(FATAL, "EndTransactionBlock: unexpected state %s", BlockStateAsString(s->blockState)); s = s->parent; } if (s->blockState == TBLOCK_INPROGRESS) s->blockState = TBLOCK_END; else elog(FATAL, "EndTransactionBlock: unexpected state %s", BlockStateAsString(s->blockState)); result = true; break;

事务状态处于TBLOCK_SUBABORT子事务中，将子事务状态改变为TBLOCK_SUBABORT，否则如果处于TBLOCK_SUBINPROGRESS则改变为TBLOCK_SUBABORT_PENDING。循环处理父事务。最后处理顶层事务将事务状态，标记result为fasle代表ROLLBACK

/* Here we are inside an aborted subtransaction. Treat the COMMIT as ROLLBACK: set up to abort everything and exit the main transaction. */ case TBLOCK_SUBABORT: while (s->parent != NULL){ if (s->blockState == TBLOCK_SUBINPROGRESS) s->blockState = TBLOCK_SUBABORT_PENDING; else if (s->blockState == TBLOCK_SUBABORT) s->blockState = TBLOCK_SUBABORT_END; else elog(FATAL, "EndTransactionBlock: unexpected state %s", BlockStateAsString(s->blockState)); s = s->parent; } if (s->blockState == TBLOCK_INPROGRESS)s->blockState = TBLOCK_ABORT_PENDING; else if (s->blockState == TBLOCK_ABORT) s->blockState = TBLOCK_ABORT_END; else elog(FATAL, "EndTransactionBlock: unexpected state %s", BlockStateAsString(s->blockState)); break;

其他事务状态属于异常处理

/* The user issued COMMIT when not inside a transaction. For * COMMIT without CHAIN, issue a WARNING, staying in * TBLOCK_STARTED state. The upcoming call to * CommitTransactionCommand() will then close the transaction and * put us back into the default state. For COMMIT AND CHAIN, * error. */ case TBLOCK_STARTED: if (chain) ereport(ERROR, (errcode(ERRCODE_NO_ACTIVE_SQL_TRANSACTION), /* translator: %s represents an SQL statement name */ errmsg("%s can only be used in transaction blocks", "COMMIT AND CHAIN"))); else ereport(WARNING, (errcode(ERRCODE_NO_ACTIVE_SQL_TRANSACTION), errmsg("there is no transaction in progress"))); result = true; break; /* The user issued a COMMIT that somehow ran inside a parallel worker. We can't cope with that. */ case TBLOCK_PARALLEL_INPROGRESS: ereport(FATAL, (errcode(ERRCODE_INVALID_TRANSACTION_STATE),errmsg("cannot commit during a parallel operation"))); break; /* These cases are invalid. */ case TBLOCK_DEFAULT: case TBLOCK_BEGIN: case TBLOCK_SUBBEGIN: case TBLOCK_END: case TBLOCK_SUBRELEASE: case TBLOCK_SUBCOMMIT: case TBLOCK_ABORT_END: case TBLOCK_SUBABORT_END: case TBLOCK_ABORT_PENDING: case TBLOCK_SUBABORT_PENDING: case TBLOCK_SUBRESTART: case TBLOCK_SUBABORT_RESTART: case TBLOCK_PREPARE: elog(FATAL, "EndTransactionBlock: unexpected state %s", BlockStateAsString(s->blockState)); break; } Assert(s->blockState == TBLOCK_STARTED || s->blockState == TBLOCK_END || s->blockState == TBLOCK_ABORT_END || s->blockState == TBLOCK_ABORT_PENDING); s->chain = chain; return result;}

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