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/*-------------------------------------------------------------------------
*
* tupconvert.c
* Tuple conversion support.
*
* These functions provide conversion between rowtypes that are logically
* equivalent but might have columns in a different order or different sets
* of dropped columns. There is some overlap of functionality with the
* executor's "junkfilter" routines, but these functions work on bare
* HeapTuples rather than TupleTableSlots.
*
* Portions Copyright (c) 1996-2018, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* src/backend/access/common/tupconvert.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#if PG_VERSION_NUM >= 90300
#include "access/htup_details.h"
#endif
#include "access/tupconvert.h"
#include "access/sysattr.h"
#include "access/xlog.h" /* RecoveryInProgress */
#include "catalog/pg_type.h" /* *OID */
#include "utils/builtins.h"
#include "utils/tqual.h" /* HeapTupleIsSurelyDead */
#include "dirtyread_tupconvert.h"
#if PG_VERSION_NUM < 100000
/* from src/include/access/tupdesc.h, introduced in 2cd708452 */
#define TupleDescAttr(tupdesc, i) ((tupdesc)->attrs[(i)])
#endif
/*
* The conversion setup routines have the following common API:
*
* The setup routine checks whether the given source and destination tuple
* descriptors are logically compatible. If not, it throws an error.
* If so, it returns NULL if they are physically compatible (ie, no conversion
* is needed), else a TupleConversionMap that can be used by do_convert_tuple
* to perform the conversion.
*
* The TupleConversionMap, if needed, is palloc'd in the caller's memory
* context. Also, the given tuple descriptors are referenced by the map,
* so they must survive as long as the map is needed.
*
* The caller must supply a suitable primary error message to be used if
* a compatibility error is thrown. Recommended coding practice is to use
* gettext_noop() on this string, so that it is translatable but won't
* actually be translated unless the error gets thrown.
*
*
* Implementation notes:
*
* The key component of a TupleConversionMap is an attrMap[] array with
* one entry per output column. This entry contains the 1-based index of
* the corresponding input column, or zero to force a NULL value (for
* a dropped output column). The TupleConversionMap also contains workspace
* arrays.
*/
/*
* Set up for tuple conversion, matching input and output columns by name.
* (Dropped columns are ignored in both input and output.) This is intended
* for use when the rowtypes are related by inheritance, so we expect an exact
* match of both type and typmod. The error messages will be a bit unhelpful
* unless both rowtypes are named composite types.
*/
TupleConversionMap *
dirtyread_convert_tuples_by_name(TupleDesc indesc,
TupleDesc outdesc,
const char *msg)
{
TupleConversionMap *map;
AttrNumber *attrMap;
int n = outdesc->natts;
int i;
bool same;
/* Verify compatibility and prepare attribute-number map */
attrMap = dirtyread_convert_tuples_by_name_map(indesc, outdesc, msg);
/*
* Check to see if the map is one-to-one, in which case we need not do a
* tuple conversion. We must also insist that both tupdescs either
* specify or don't specify an OID column, else we need a conversion to
* add/remove space for that. (For some callers, presence or absence of
* an OID column perhaps would not really matter, but let's be safe.)
*/
if (indesc->natts == outdesc->natts &&
indesc->tdhasoid == outdesc->tdhasoid)
{
same = true;
for (i = 0; i < n; i++)
{
Form_pg_attribute inatt;
Form_pg_attribute outatt;
if (attrMap[i] == (i + 1))
continue;
/*
* If it's a dropped column and the corresponding input column is
* also dropped, we needn't convert. However, attlen and attalign
* must agree.
*/
inatt = TupleDescAttr(indesc, i);
outatt = TupleDescAttr(outdesc, i);
if (attrMap[i] == 0 &&
inatt->attisdropped &&
inatt->attlen == outatt->attlen &&
inatt->attalign == outatt->attalign)
continue;
same = false;
break;
}
}
else
same = false;
if (same)
{
/* Runtime conversion is not needed */
elog(DEBUG1, "tuple conversion is not needed");
pfree(attrMap);
return NULL;
}
/* Prepare the map structure */
map = (TupleConversionMap *) palloc(sizeof(TupleConversionMap));
map->indesc = indesc;
map->outdesc = outdesc;
map->attrMap = attrMap;
/* preallocate workspace for Datum arrays */
map->outvalues = (Datum *) palloc(n * sizeof(Datum));
map->outisnull = (bool *) palloc(n * sizeof(bool));
n = indesc->natts + 1; /* +1 for NULL */
map->invalues = (Datum *) palloc(n * sizeof(Datum));
map->inisnull = (bool *) palloc(n * sizeof(bool));
map->invalues[0] = (Datum) 0; /* set up the NULL entry */
map->inisnull[0] = true;
return map;
}
static const struct system_columns_t {
char *attname;
Oid atttypid;
int32 atttypmod;
int attnum;
} system_columns[] = {
{ "ctid", TIDOID, -1, SelfItemPointerAttributeNumber },
{ "oid", OIDOID, -1, ObjectIdAttributeNumber },
{ "xmin", XIDOID, -1, MinTransactionIdAttributeNumber },
{ "cmin", CIDOID, -1, MinCommandIdAttributeNumber },
{ "xmax", XIDOID, -1, MaxTransactionIdAttributeNumber },
{ "cmax", CIDOID, -1, MaxCommandIdAttributeNumber },
{ "tableoid", OIDOID, -1, TableOidAttributeNumber },
{ "dead", BOOLOID, -1, DeadFakeAttributeNumber }, /* fake column to return HeapTupleIsSurelyDead */
{ 0 },
};
/*
* Return a palloc'd bare attribute map for tuple conversion, matching input
* and output columns by name. (Dropped columns are ignored in both input and
* output.) This is normally a subroutine for convert_tuples_by_name, but can
* be used standalone.
*
* This version from dirtyread_tupconvert.c adds the ability to retrieve dropped
* columns by requesting "dropped_N" as output column, where N is the attnum.
*/
AttrNumber *
dirtyread_convert_tuples_by_name_map(TupleDesc indesc,
TupleDesc outdesc,
const char *msg)
{
AttrNumber *attrMap;
int n;
int i;
n = outdesc->natts;
attrMap = (AttrNumber *) palloc0(n * sizeof(AttrNumber));
for (i = 0; i < n; i++)
{
Form_pg_attribute outatt = TupleDescAttr(outdesc, i);
char *attname;
Oid atttypid;
int32 atttypmod;
int j;
if (outatt->attisdropped)
continue; /* attrMap[i] is already 0 */
attname = NameStr(outatt->attname);
atttypid = outatt->atttypid;
atttypmod = outatt->atttypmod;
for (j = 0; j < indesc->natts; j++)
{
Form_pg_attribute inatt = TupleDescAttr(indesc, j);
if (inatt->attisdropped)
continue;
if (strcmp(attname, NameStr(inatt->attname)) == 0)
{
/* Found it, check type */
if (atttypid != inatt->atttypid || atttypmod != inatt->atttypmod)
ereport(ERROR,
(errcode(ERRCODE_DATATYPE_MISMATCH),
errmsg_internal("%s", _(msg)),
errdetail("Attribute \"%s\" has type %s in corresponding attribute of type %s.",
attname,
format_type_with_typemod(inatt->atttypid, inatt->atttypmod),
format_type_be(indesc->tdtypeid))));
attrMap[i] = (AttrNumber) (j + 1);
break;
}
}
/* Check dropped columns */
if (attrMap[i] == 0)
if (strncmp(attname, "dropped_", sizeof("dropped_") - 1) == 0)
{
Form_pg_attribute inatt;
j = atoi(attname + sizeof("dropped_") - 1);
if (j < 1 || j > indesc->natts)
ereport(ERROR,
(errcode(ERRCODE_DATATYPE_MISMATCH),
errmsg_internal("%s", _(msg)),
errdetail("Attribute \"%s\" index is out of range 1 .. %d.",
attname, indesc->natts)));
inatt = TupleDescAttr(indesc, j - 1);
if (! inatt->attisdropped)
ereport(ERROR,
(errcode(ERRCODE_DATATYPE_MISMATCH),
errmsg_internal("%s", _(msg)),
errdetail("Attribute %d is not a dropped column.", j)));
if (outatt->attlen != inatt->attlen)
ereport(ERROR,
(errcode(ERRCODE_DATATYPE_MISMATCH),
errmsg_internal("%s", _(msg)),
errdetail("Type length of dropped column \"%s\" was %d.",
attname, inatt->attlen)));
if (outatt->attbyval != inatt->attbyval)
ereport(ERROR,
(errcode(ERRCODE_DATATYPE_MISMATCH),
errmsg_internal("%s", _(msg)),
errdetail("\"By value\" of dropped column \"%s\" does not match.",
attname)));
if (outatt->attalign != inatt->attalign)
ereport(ERROR,
(errcode(ERRCODE_DATATYPE_MISMATCH),
errmsg_internal("%s", _(msg)),
errdetail("Alignment of dropped column \"%s\" was %c.",
attname, inatt->attalign)));
inatt->atttypid = atttypid;
if (atttypmod != inatt->atttypmod)
ereport(ERROR,
(errcode(ERRCODE_DATATYPE_MISMATCH),
errmsg_internal("%s", _(msg)),
errdetail("Type modifier of dropped column \"%s\" was %s.",
attname,
format_type_with_typemod(inatt->atttypid, inatt->atttypmod))));
attrMap[i] = (AttrNumber) j;
}
/* Check system columns */
if (attrMap[i] == 0)
for (j = 0; system_columns[j].attname; j++)
if (strcmp(attname, system_columns[j].attname) == 0)
{
/* Found it, check type */
if (atttypid != system_columns[j].atttypid || atttypmod != system_columns[j].atttypmod)
ereport(ERROR,
(errcode(ERRCODE_DATATYPE_MISMATCH),
errmsg_internal("%s", _(msg)),
errdetail("Attribute \"%s\" has type %s in corresponding attribute of type %s.",
attname,
format_type_be(system_columns[j].atttypid),
format_type_be(indesc->tdtypeid))));
/* GetOldestXmin() is not available during recovery */
if (system_columns[j].attnum == DeadFakeAttributeNumber &&
RecoveryInProgress())
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("Cannot use \"dead\" column during recovery")));
attrMap[i] = system_columns[j].attnum;
break;
}
if (attrMap[i] == 0)
ereport(ERROR,
(errcode(ERRCODE_DATATYPE_MISMATCH),
errmsg_internal("%s", _(msg)),
errdetail("Attribute \"%s\" does not exist in type %s.",
attname,
format_type_be(indesc->tdtypeid))));
}
return attrMap;
}
/*
* Perform conversion of a tuple according to the map.
*/
HeapTuple
dirtyread_do_convert_tuple(HeapTuple tuple, TupleConversionMap *map, TransactionId oldest_xmin)
{
AttrNumber *attrMap = map->attrMap;
Datum *invalues = map->invalues;
bool *inisnull = map->inisnull;
Datum *outvalues = map->outvalues;
bool *outisnull = map->outisnull;
int outnatts = map->outdesc->natts;
int i;
/*
* Extract all the values of the old tuple, offsetting the arrays so that
* invalues[0] is left NULL and invalues[1] is the first source attribute;
* this exactly matches the numbering convention in attrMap.
*/
heap_deform_tuple(tuple, map->indesc, invalues + 1, inisnull + 1);
/*
* Transpose into proper fields of the new tuple.
*/
for (i = 0; i < outnatts; i++)
{
int j = attrMap[i];
if (j == DeadFakeAttributeNumber)
{
outvalues[i] = HeapTupleIsSurelyDead(tuple
#if PG_VERSION_NUM < 90400
->t_data
#endif
, oldest_xmin);
outisnull[i] = false;
}
else if (j < 0)
outvalues[i] = heap_getsysattr(tuple, j, map->indesc, &outisnull[i]);
else
{
outvalues[i] = invalues[j];
outisnull[i] = inisnull[j];
}
}
/*
* Now form the new tuple.
*/
return heap_form_tuple(map->outdesc, outvalues, outisnull);
}
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