tupdesc.c

postgresql8.3.4源码,开源数据库

/*-------------------------------------------------------------------------
 *
 * tupdesc.c
 *	  POSTGRES tuple descriptor support code
 *
 * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $PostgreSQL: pgsql/src/backend/access/common/tupdesc.c,v 1.122 2008/01/01 19:45:46 momjian Exp $
 *
 * NOTES
 *	  some of the executor utility code such as "ExecTypeFromTL" should be
 *	  moved here.
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include "catalog/pg_type.h"
#include "parser/parse_type.h"
#include "utils/builtins.h"
#include "utils/resowner.h"
#include "utils/syscache.h"


/*
 * CreateTemplateTupleDesc
 *		This function allocates an empty tuple descriptor structure.
 *
 * Tuple type ID information is initially set for an anonymous record type;
 * caller can overwrite this if needed.
 */
TupleDesc
CreateTemplateTupleDesc(int natts, bool hasoid)
{
	TupleDesc	desc;
	char	   *stg;
	int			attroffset;

	/*
	 * sanity checks
	 */
	AssertArg(natts >= 0);

	/*
	 * Allocate enough memory for the tuple descriptor, including the
	 * attribute rows, and set up the attribute row pointers.
	 *
	 * Note: we assume that sizeof(struct tupleDesc) is a multiple of the
	 * struct pointer alignment requirement, and hence we don't need to insert
	 * alignment padding between the struct and the array of attribute row
	 * pointers.
	 */
	attroffset = sizeof(struct tupleDesc) + natts * sizeof(Form_pg_attribute);
	attroffset = MAXALIGN(attroffset);
	stg = palloc(attroffset + natts * MAXALIGN(ATTRIBUTE_TUPLE_SIZE));
	desc = (TupleDesc) stg;

	if (natts > 0)
	{
		Form_pg_attribute *attrs;
		int			i;

		attrs = (Form_pg_attribute *) (stg + sizeof(struct tupleDesc));
		desc->attrs = attrs;
		stg += attroffset;
		for (i = 0; i < natts; i++)
		{
			attrs[i] = (Form_pg_attribute) stg;
			stg += MAXALIGN(ATTRIBUTE_TUPLE_SIZE);
		}
	}
	else
		desc->attrs = NULL;

	/*
	 * Initialize other fields of the tupdesc.
	 */
	desc->natts = natts;
	desc->constr = NULL;
	desc->tdtypeid = RECORDOID;
	desc->tdtypmod = -1;
	desc->tdhasoid = hasoid;
	desc->tdrefcount = -1;		/* assume not reference-counted */

	return desc;
}

/*
 * CreateTupleDesc
 *		This function allocates a new TupleDesc pointing to a given
 *		Form_pg_attribute array.
 *
 * Note: if the TupleDesc is ever freed, the Form_pg_attribute array
 * will not be freed thereby.
 *
 * Tuple type ID information is initially set for an anonymous record type;
 * caller can overwrite this if needed.
 */
TupleDesc
CreateTupleDesc(int natts, bool hasoid, Form_pg_attribute *attrs)
{
	TupleDesc	desc;

	/*
	 * sanity checks
	 */
	AssertArg(natts >= 0);

	desc = (TupleDesc) palloc(sizeof(struct tupleDesc));
	desc->attrs = attrs;
	desc->natts = natts;
	desc->constr = NULL;
	desc->tdtypeid = RECORDOID;
	desc->tdtypmod = -1;
	desc->tdhasoid = hasoid;
	desc->tdrefcount = -1;		/* assume not reference-counted */

	return desc;
}

/*
 * CreateTupleDescCopy
 *		This function creates a new TupleDesc by copying from an existing
 *		TupleDesc.
 *
 * !!! Constraints and defaults are not copied !!!
 */
TupleDesc
CreateTupleDescCopy(TupleDesc tupdesc)
{
	TupleDesc	desc;
	int			i;

	desc = CreateTemplateTupleDesc(tupdesc->natts, tupdesc->tdhasoid);

	for (i = 0; i < desc->natts; i++)
	{
		memcpy(desc->attrs[i], tupdesc->attrs[i], ATTRIBUTE_TUPLE_SIZE);
		desc->attrs[i]->attnotnull = false;
		desc->attrs[i]->atthasdef = false;
	}

	desc->tdtypeid = tupdesc->tdtypeid;
	desc->tdtypmod = tupdesc->tdtypmod;

	return desc;
}

/*
 * CreateTupleDescCopyConstr
 *		This function creates a new TupleDesc by copying from an existing
 *		TupleDesc (including its constraints and defaults).
 */
TupleDesc
CreateTupleDescCopyConstr(TupleDesc tupdesc)
{
	TupleDesc	desc;
	TupleConstr *constr = tupdesc->constr;
	int			i;

	desc = CreateTemplateTupleDesc(tupdesc->natts, tupdesc->tdhasoid);

	for (i = 0; i < desc->natts; i++)
	{
		memcpy(desc->attrs[i], tupdesc->attrs[i], ATTRIBUTE_TUPLE_SIZE);
	}

	if (constr)
	{
		TupleConstr *cpy = (TupleConstr *) palloc0(sizeof(TupleConstr));

		cpy->has_not_null = constr->has_not_null;

		if ((cpy->num_defval = constr->num_defval) > 0)
		{
			cpy->defval = (AttrDefault *) palloc(cpy->num_defval * sizeof(AttrDefault));
			memcpy(cpy->defval, constr->defval, cpy->num_defval * sizeof(AttrDefault));
			for (i = cpy->num_defval - 1; i >= 0; i--)
			{
				if (constr->defval[i].adbin)
					cpy->defval[i].adbin = pstrdup(constr->defval[i].adbin);
			}
		}

		if ((cpy->num_check = constr->num_check) > 0)
		{
			cpy->check = (ConstrCheck *) palloc(cpy->num_check * sizeof(ConstrCheck));
			memcpy(cpy->check, constr->check, cpy->num_check * sizeof(ConstrCheck));
			for (i = cpy->num_check - 1; i >= 0; i--)
			{
				if (constr->check[i].ccname)
					cpy->check[i].ccname = pstrdup(constr->check[i].ccname);
				if (constr->check[i].ccbin)
					cpy->check[i].ccbin = pstrdup(constr->check[i].ccbin);
			}
		}

		desc->constr = cpy;
	}

	desc->tdtypeid = tupdesc->tdtypeid;
	desc->tdtypmod = tupdesc->tdtypmod;

	return desc;
}

/*
 * Free a TupleDesc including all substructure
 */
void
FreeTupleDesc(TupleDesc tupdesc)
{
	int			i;

	/*
	 * Possibly this should assert tdrefcount == 0, to disallow explicit
	 * freeing of un-refcounted tupdescs?
	 */
	Assert(tupdesc->tdrefcount <= 0);

	if (tupdesc->constr)
	{
		if (tupdesc->constr->num_defval > 0)
		{
			AttrDefault *attrdef = tupdesc->constr->defval;

			for (i = tupdesc->constr->num_defval - 1; i >= 0; i--)
			{
				if (attrdef[i].adbin)
					pfree(attrdef[i].adbin);
			}
			pfree(attrdef);
		}
		if (tupdesc->constr->num_check > 0)
		{
			ConstrCheck *check = tupdesc->constr->check;

			for (i = tupdesc->constr->num_check - 1; i >= 0; i--)
			{
				if (check[i].ccname)
					pfree(check[i].ccname);
				if (check[i].ccbin)
					pfree(check[i].ccbin);
			}
			pfree(check);
		}
		pfree(tupdesc->constr);
	}

	pfree(tupdesc);
}

/*
 * Increment the reference count of a tupdesc, and log the reference in
 * CurrentResourceOwner.
 *
 * Do not apply this to tupdescs that are not being refcounted.  (Use the
 * macro PinTupleDesc for tupdescs of uncertain status.)
 */
void
IncrTupleDescRefCount(TupleDesc tupdesc)
{
	Assert(tupdesc->tdrefcount >= 0);

	ResourceOwnerEnlargeTupleDescs(CurrentResourceOwner);
	tupdesc->tdrefcount++;
	ResourceOwnerRememberTupleDesc(CurrentResourceOwner, tupdesc);
}

/*
 * Decrement the reference count of a tupdesc, remove the corresponding
 * reference from CurrentResourceOwner, and free the tupdesc if no more
 * references remain.
 *
 * Do not apply this to tupdescs that are not being refcounted.  (Use the
 * macro ReleaseTupleDesc for tupdescs of uncertain status.)
 */
void
DecrTupleDescRefCount(TupleDesc tupdesc)
{
	Assert(tupdesc->tdrefcount > 0);

	ResourceOwnerForgetTupleDesc(CurrentResourceOwner, tupdesc);
	if (--tupdesc->tdrefcount == 0)
		FreeTupleDesc(tupdesc);
}

/*
 * Compare two TupleDesc structures for logical equality
 *
 * Note: we deliberately do not check the attrelid and tdtypmod fields.
 * This allows typcache.c to use this routine to see if a cached record type
 * matches a requested type, and is harmless for relcache.c's uses.
 * We don't compare tdrefcount, either.
 */
bool
equalTupleDescs(TupleDesc tupdesc1, TupleDesc tupdesc2)
{
	int			i,
				j,
				n;

	if (tupdesc1->natts != tupdesc2->natts)
		return false;
	if (tupdesc1->tdtypeid != tupdesc2->tdtypeid)
		return false;
	if (tupdesc1->tdhasoid != tupdesc2->tdhasoid)
		return false;

	for (i = 0; i < tupdesc1->natts; i++)
	{
		Form_pg_attribute attr1 = tupdesc1->attrs[i];
		Form_pg_attribute attr2 = tupdesc2->attrs[i];

		/*
		 * We do not need to check every single field here: we can disregard
		 * attrelid and attnum (which were used to place the row in the attrs
		 * array in the first place).  It might look like we could dispense
		 * with checking attlen/attbyval/attalign, since these are derived
		 * from atttypid; but in the case of dropped columns we must check
		 * them (since atttypid will be zero for all dropped columns) and in
		 * general it seems safer to check them always.