greenplumn constraint 源码

greenplumn constraint 代码

文件路径：/src/backend/commands/constraint.c

/*-------------------------------------------------------------------------
 *
 * constraint.c
 *	  PostgreSQL CONSTRAINT support code.
 *
 * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *	  src/backend/commands/constraint.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/genam.h"
#include "access/heapam.h"
#include "access/tableam.h"
#include "catalog/index.h"
#include "commands/trigger.h"
#include "executor/executor.h"
#include "utils/builtins.h"
#include "utils/rel.h"
#include "utils/snapmgr.h"


/*
 * unique_key_recheck - trigger function to do a deferred uniqueness check.
 *
 * This now also does deferred exclusion-constraint checks, so the name is
 * somewhat historical.
 *
 * This is invoked as an AFTER ROW trigger for both INSERT and UPDATE,
 * for any rows recorded as potentially violating a deferrable unique
 * or exclusion constraint.
 *
 * This may be an end-of-statement check, a commit-time check, or a
 * check triggered by a SET CONSTRAINTS command.
 */
Datum
unique_key_recheck(PG_FUNCTION_ARGS)
{
	TriggerData *trigdata = castNode(TriggerData, fcinfo->context);
	const char *funcname = "unique_key_recheck";
	ItemPointerData checktid;
	ItemPointerData tmptid;
	Relation	indexRel;
	IndexInfo  *indexInfo;
	EState	   *estate;
	ExprContext *econtext;
	TupleTableSlot *slot;
	Datum		values[INDEX_MAX_KEYS];
	bool		isnull[INDEX_MAX_KEYS];

	/*
	 * Make sure this is being called as an AFTER ROW trigger.  Note:
	 * translatable error strings are shared with ri_triggers.c, so resist the
	 * temptation to fold the function name into them.
	 */
	if (!CALLED_AS_TRIGGER(fcinfo))
		ereport(ERROR,
				(errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
				 errmsg("function \"%s\" was not called by trigger manager",
						funcname)));

	if (!TRIGGER_FIRED_AFTER(trigdata->tg_event) ||
		!TRIGGER_FIRED_FOR_ROW(trigdata->tg_event))
		ereport(ERROR,
				(errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
				 errmsg("function \"%s\" must be fired AFTER ROW",
						funcname)));

	/*
	 * Get the new data that was inserted/updated.
	 */
	if (TRIGGER_FIRED_BY_INSERT(trigdata->tg_event))
		checktid = trigdata->tg_trigslot->tts_tid;
	else if (TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event))
		checktid = trigdata->tg_newslot->tts_tid;
	else
	{
		ereport(ERROR,
				(errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
				 errmsg("function \"%s\" must be fired for INSERT or UPDATE",
						funcname)));
		ItemPointerSetInvalid(&checktid);	/* keep compiler quiet */
	}

	slot = table_slot_create(trigdata->tg_relation, NULL);

	/*
	 * If the row pointed at by checktid is now dead (ie, inserted and then
	 * deleted within our transaction), we can skip the check.  However, we
	 * have to be careful, because this trigger gets queued only in response
	 * to index insertions; which means it does not get queued e.g. for HOT
	 * updates.  The row we are called for might now be dead, but have a live
	 * HOT child, in which case we still need to make the check ---
	 * effectively, we're applying the check against the live child row,
	 * although we can use the values from this row since by definition all
	 * columns of interest to us are the same.
	 *
	 * This might look like just an optimization, because the index AM will
	 * make this identical test before throwing an error.  But it's actually
	 * needed for correctness, because the index AM will also throw an error
	 * if it doesn't find the index entry for the row.  If the row's dead then
	 * it's possible the index entry has also been marked dead, and even
	 * removed.
	 */
	tmptid = checktid;
	{
		IndexFetchTableData *scan = table_index_fetch_begin(trigdata->tg_relation);
		bool		call_again = false;

		if (!table_index_fetch_tuple(scan, &tmptid, SnapshotSelf, slot,
									 &call_again, NULL))
		{
			/*
			 * All rows referenced by the index entry are dead, so skip the
			 * check.
			 */
			ExecDropSingleTupleTableSlot(slot);
			table_index_fetch_end(scan);
			return PointerGetDatum(NULL);
		}
		table_index_fetch_end(scan);
	}

	/*
	 * Open the index, acquiring a RowExclusiveLock, just as if we were going
	 * to update it.  (This protects against possible changes of the index
	 * schema, not against concurrent updates.)
	 */
	indexRel = index_open(trigdata->tg_trigger->tgconstrindid,
						  RowExclusiveLock);
	indexInfo = BuildIndexInfo(indexRel);

	/*
	 * Typically the index won't have expressions, but if it does we need an
	 * EState to evaluate them.  We need it for exclusion constraints too,
	 * even if they are just on simple columns.
	 */
	if (indexInfo->ii_Expressions != NIL ||
		indexInfo->ii_ExclusionOps != NULL)
	{
		estate = CreateExecutorState();
		econtext = GetPerTupleExprContext(estate);
		econtext->ecxt_scantuple = slot;
	}
	else
		estate = NULL;

	/*
	 * Form the index values and isnull flags for the index entry that we need
	 * to check.
	 *
	 * Note: if the index uses functions that are not as immutable as they are
	 * supposed to be, this could produce an index tuple different from the
	 * original.  The index AM can catch such errors by verifying that it
	 * finds a matching index entry with the tuple's TID.  For exclusion
	 * constraints we check this in check_exclusion_constraint().
	 */
	FormIndexDatum(indexInfo, slot, estate, values, isnull);

	/*
	 * Now do the appropriate check.
	 */
	if (indexInfo->ii_ExclusionOps == NULL)
	{
		/*
		 * Note: this is not a real insert; it is a check that the index entry
		 * that has already been inserted is unique.  Passing the tuple's tid
		 * (i.e. unmodified by table_index_fetch_tuple()) is correct even if
		 * the row is now dead, because that is the TID the index will know
		 * about.
		 */
		index_insert(indexRel, values, isnull, &checktid,
					 trigdata->tg_relation, UNIQUE_CHECK_EXISTING,
					 indexInfo);
	}
	else
	{
		/*
		 * For exclusion constraints we just do the normal check, but now it's
		 * okay to throw error.  In the HOT-update case, we must use the live
		 * HOT child's TID here, else check_exclusion_constraint will think
		 * the child is a conflict.
		 */
		check_exclusion_constraint(trigdata->tg_relation, indexRel, indexInfo,
								   &tmptid, values, isnull,
								   estate, false);
	}

	/*
	 * If that worked, then this index entry is unique or non-excluded, and we
	 * are done.
	 */
	if (estate != NULL)
		FreeExecutorState(estate);

	ExecDropSingleTupleTableSlot(slot);

	index_close(indexRel, RowExclusiveLock);

	return PointerGetDatum(NULL);
}

相关信息

greenplumn 源码目录

相关文章

greenplumn aggregatecmds 源码

greenplumn alter 源码

greenplumn amcmds 源码

greenplumn analyze 源码

greenplumn analyzefuncs 源码

greenplumn analyzeutils 源码

greenplumn async 源码

greenplumn cluster 源码

greenplumn collationcmds 源码

greenplumn comment 源码