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postgresql/src/backend/access/heap/tuptoaster.c

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/*-------------------------------------------------------------------------
*
* tuptoaster.c
* Support routines for external and compressed storage of
* variable size attributes.
*
* Copyright (c) 2000-2002, PostgreSQL Global Development Group
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/access/heap/tuptoaster.c,v 1.27 2002/01/16 20:29:01 tgl Exp $
*
*
* INTERFACE ROUTINES
* heap_tuple_toast_attrs -
* Try to make a given tuple fit into one page by compressing
* or moving off attributes
*
* heap_tuple_untoast_attr -
* Fetch back a given value from the "secondary" relation
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include <unistd.h>
#include <fcntl.h>
#include "access/heapam.h"
#include "access/genam.h"
#include "access/tuptoaster.h"
#include "catalog/catalog.h"
#include "utils/rel.h"
#include "utils/builtins.h"
#include "utils/fmgroids.h"
#include "utils/pg_lzcompress.h"
#ifdef TUPLE_TOASTER_ACTIVE
#undef TOAST_DEBUG
static void toast_delete(Relation rel, HeapTuple oldtup);
static void toast_delete_datum(Relation rel, Datum value);
static void toast_insert_or_update(Relation rel, HeapTuple newtup,
HeapTuple oldtup);
static Datum toast_save_datum(Relation rel, Datum value);
static varattrib *toast_fetch_datum(varattrib *attr);
/* ----------
* heap_tuple_toast_attrs -
*
* This is the central public entry point for toasting from heapam.
*
* Calls the appropriate event specific action.
* ----------
*/
void
heap_tuple_toast_attrs(Relation rel, HeapTuple newtup, HeapTuple oldtup)
{
if (newtup == NULL)
toast_delete(rel, oldtup);
else
toast_insert_or_update(rel, newtup, oldtup);
}
/* ----------
* heap_tuple_fetch_attr -
*
* Public entry point to get back a toasted value
* external storage (possibly still in compressed format).
* ----------
*/
varattrib *
heap_tuple_fetch_attr(varattrib *attr)
{
varattrib *result;
if (VARATT_IS_EXTERNAL(attr))
{
/*
* This is an external stored plain value
*/
result = toast_fetch_datum(attr);
}
else
{
/*
* This is a plain value inside of the main tuple - why am I
* called?
*/
result = attr;
}
return result;
}
/* ----------
* heap_tuple_untoast_attr -
*
* Public entry point to get back a toasted value from compression
* or external storage.
* ----------
*/
varattrib *
heap_tuple_untoast_attr(varattrib *attr)
{
varattrib *result;
if (VARATT_IS_EXTERNAL(attr))
{
if (VARATT_IS_COMPRESSED(attr))
{
/* ----------
* This is an external stored compressed value
* Fetch it from the toast heap and decompress.
* ----------
*/
varattrib *tmp;
tmp = toast_fetch_datum(attr);
result = (varattrib *) palloc(attr->va_content.va_external.va_rawsize
+ VARHDRSZ);
VARATT_SIZEP(result) = attr->va_content.va_external.va_rawsize
+ VARHDRSZ;
pglz_decompress((PGLZ_Header *) tmp, VARATT_DATA(result));
pfree(tmp);
}
else
{
/*
* This is an external stored plain value
*/
result = toast_fetch_datum(attr);
}
}
else if (VARATT_IS_COMPRESSED(attr))
{
/*
* This is a compressed value inside of the main tuple
*/
result = (varattrib *) palloc(attr->va_content.va_compressed.va_rawsize
+ VARHDRSZ);
VARATT_SIZEP(result) = attr->va_content.va_compressed.va_rawsize
+ VARHDRSZ;
pglz_decompress((PGLZ_Header *) attr, VARATT_DATA(result));
}
else
/*
* This is a plain value inside of the main tuple - why am I
* called?
*/
return attr;
return result;
}
/* ----------
* toast_raw_datum_size -
*
* Return the raw (detoasted) size of a varlena datum
* ----------
*/
Size
toast_raw_datum_size(Datum value)
{
varattrib *attr = (varattrib *) DatumGetPointer(value);
Size result;
if (VARATT_IS_COMPRESSED(attr))
{
/*
* va_rawsize shows the original data size, whether the datum is
* external or not.
*/
result = attr->va_content.va_compressed.va_rawsize + VARHDRSZ;
}
else if (VARATT_IS_EXTERNAL(attr))
{
/*
* an uncompressed external attribute has rawsize including the
* header (not too consistent!)
*/
result = attr->va_content.va_external.va_rawsize;
}
else
{
/* plain untoasted datum */
result = VARSIZE(attr);
}
return result;
}
/* ----------
* toast_delete -
*
* Cascaded delete toast-entries on DELETE
* ----------
*/
static void
toast_delete(Relation rel, HeapTuple oldtup)
{
TupleDesc tupleDesc;
Form_pg_attribute *att;
int numAttrs;
int i;
Datum value;
bool isnull;
/*
* Get the tuple descriptor, the number of and attribute descriptors.
*/
tupleDesc = rel->rd_att;
numAttrs = tupleDesc->natts;
att = tupleDesc->attrs;
/*
* Check for external stored attributes and delete them from the
* secondary relation.
*/
for (i = 0; i < numAttrs; i++)
{
if (att[i]->attlen == -1)
{
value = heap_getattr(oldtup, i + 1, tupleDesc, &isnull);
if (!isnull && VARATT_IS_EXTERNAL(value))
toast_delete_datum(rel, value);
}
}
}
/* ----------
* toast_insert_or_update -
*
* Delete no-longer-used toast-entries and create new ones to
* make the new tuple fit on INSERT or UPDATE
* ----------
*/
static void
toast_insert_or_update(Relation rel, HeapTuple newtup, HeapTuple oldtup)
{
TupleDesc tupleDesc;
Form_pg_attribute *att;
int numAttrs;
int i;
bool old_isnull;
bool new_isnull;
bool need_change = false;
bool need_free = false;
bool need_delold = false;
bool has_nulls = false;
Size maxDataLen;
char toast_action[MaxHeapAttributeNumber];
char toast_nulls[MaxHeapAttributeNumber];
Datum toast_values[MaxHeapAttributeNumber];
int32 toast_sizes[MaxHeapAttributeNumber];
bool toast_free[MaxHeapAttributeNumber];
bool toast_delold[MaxHeapAttributeNumber];
/*
* Get the tuple descriptor, the number of and attribute descriptors
* and the location of the tuple values.
*/
tupleDesc = rel->rd_att;
numAttrs = tupleDesc->natts;
att = tupleDesc->attrs;
/* ----------
* Then collect information about the values given
*
* NOTE: toast_action[i] can have these values:
* ' ' default handling
* 'p' already processed --- don't touch it
* 'x' incompressible, but OK to move off
* ----------
*/
memset(toast_action, ' ', numAttrs * sizeof(char));
memset(toast_nulls, ' ', numAttrs * sizeof(char));
memset(toast_free, 0, numAttrs * sizeof(bool));
memset(toast_delold, 0, numAttrs * sizeof(bool));
for (i = 0; i < numAttrs; i++)
{
varattrib *old_value;
varattrib *new_value;
if (oldtup != NULL)
{
/*
* For UPDATE get the old and new values of this attribute
*/
old_value = (varattrib *) DatumGetPointer(
heap_getattr(oldtup, i + 1, tupleDesc, &old_isnull));
toast_values[i] =
heap_getattr(newtup, i + 1, tupleDesc, &new_isnull);
new_value = (varattrib *) DatumGetPointer(toast_values[i]);
/*
* If the old value is an external stored one, check if it has
* changed so we have to delete it later.
*/
if (!old_isnull && att[i]->attlen == -1 &&
VARATT_IS_EXTERNAL(old_value))
{
if (new_isnull || !VARATT_IS_EXTERNAL(new_value) ||
old_value->va_content.va_external.va_valueid !=
new_value->va_content.va_external.va_valueid ||
old_value->va_content.va_external.va_toastrelid !=
new_value->va_content.va_external.va_toastrelid)
{
/*
* The old external store value isn't needed any more
* after the update
*/
toast_delold[i] = true;
need_delold = true;
}
else
{
/*
* This attribute isn't changed by this update so we
* reuse the original reference to the old value in
* the new tuple.
*/
toast_action[i] = 'p';
toast_sizes[i] = VARATT_SIZE(toast_values[i]);
continue;
}
}
}
else
{
/*
* For INSERT simply get the new value
*/
toast_values[i] =
heap_getattr(newtup, i + 1, tupleDesc, &new_isnull);
}
/*
* Handle NULL attributes
*/
if (new_isnull)
{
toast_action[i] = 'p';
toast_nulls[i] = 'n';
has_nulls = true;
continue;
}
/*
* Now look at varsize attributes
*/
if (att[i]->attlen == -1)
{
/*
* If the table's attribute says PLAIN always, force it so.
*/
if (att[i]->attstorage == 'p')
toast_action[i] = 'p';
/*
* We took care of UPDATE above, so any external value we find
* still in the tuple must be someone else's we cannot reuse.
* Expand it to plain (and, probably, toast it again below).
*/
if (VARATT_IS_EXTERNAL(DatumGetPointer(toast_values[i])))
{
toast_values[i] = PointerGetDatum(heap_tuple_untoast_attr(
(varattrib *) DatumGetPointer(toast_values[i])));
toast_free[i] = true;
need_change = true;
need_free = true;
}
/*
* Remember the size of this attribute
*/
toast_sizes[i] = VARATT_SIZE(DatumGetPointer(toast_values[i]));
}
else
{
/*
* Not a variable size attribute, plain storage always
*/
toast_action[i] = 'p';
toast_sizes[i] = att[i]->attlen;
}
}
/* ----------
* Compress and/or save external until data fits into target length
*
* 1: Inline compress attributes with attstorage 'x'
* 2: Store attributes with attstorage 'x' or 'e' external
* 3: Inline compress attributes with attstorage 'm'
* 4: Store attributes with attstorage 'm' external
* ----------
*/
maxDataLen = offsetof(HeapTupleHeaderData, t_bits);
if (has_nulls)
maxDataLen += BITMAPLEN(numAttrs);
maxDataLen = TOAST_TUPLE_TARGET - MAXALIGN(maxDataLen);
/*
* Look for attributes with attstorage 'x' to compress
*/
while (MAXALIGN(ComputeDataSize(tupleDesc, toast_values, toast_nulls)) >
maxDataLen)
{
int biggest_attno = -1;
int32 biggest_size = MAXALIGN(sizeof(varattrib));
Datum old_value;
Datum new_value;
/*
* Search for the biggest yet uncompressed internal attribute
*/
for (i = 0; i < numAttrs; i++)
{
if (toast_action[i] != ' ')
continue;
if (VARATT_IS_EXTENDED(toast_values[i]))
continue;
if (att[i]->attstorage != 'x')
continue;
if (toast_sizes[i] > biggest_size)
{
biggest_attno = i;
biggest_size = toast_sizes[i];
}
}
if (biggest_attno < 0)
break;
/*
* Attempt to compress it inline
*/
i = biggest_attno;
old_value = toast_values[i];
new_value = toast_compress_datum(old_value);
if (DatumGetPointer(new_value) != NULL)
{
/* successful compression */
if (toast_free[i])
pfree(DatumGetPointer(old_value));
toast_values[i] = new_value;
toast_free[i] = true;
toast_sizes[i] = VARATT_SIZE(toast_values[i]);
need_change = true;
need_free = true;
}
else
{
/*
* incompressible data, ignore on subsequent compression
* passes
*/
toast_action[i] = 'x';
}
}
/*
* Second we look for attributes of attstorage 'x' or 'e' that are
* still inline.
*/
while (MAXALIGN(ComputeDataSize(tupleDesc, toast_values, toast_nulls)) >
maxDataLen && rel->rd_rel->reltoastrelid != InvalidOid)
{
int biggest_attno = -1;
int32 biggest_size = MAXALIGN(sizeof(varattrib));
Datum old_value;
/*------
* Search for the biggest yet inlined attribute with
* attstorage equals 'x' or 'e'
*------
*/
for (i = 0; i < numAttrs; i++)
{
if (toast_action[i] == 'p')
continue;
if (VARATT_IS_EXTERNAL(toast_values[i]))
continue;
if (att[i]->attstorage != 'x' && att[i]->attstorage != 'e')
continue;
if (toast_sizes[i] > biggest_size)
{
biggest_attno = i;
biggest_size = toast_sizes[i];
}
}
if (biggest_attno < 0)
break;
/*
* Store this external
*/
i = biggest_attno;
old_value = toast_values[i];
toast_action[i] = 'p';
toast_values[i] = toast_save_datum(rel, toast_values[i]);
if (toast_free[i])
pfree(DatumGetPointer(old_value));
toast_free[i] = true;
toast_sizes[i] = VARATT_SIZE(toast_values[i]);
need_change = true;
need_free = true;
}
/*
* Round 3 - this time we take attributes with storage 'm' into
* compression
*/
while (MAXALIGN(ComputeDataSize(tupleDesc, toast_values, toast_nulls)) >
maxDataLen)
{
int biggest_attno = -1;
int32 biggest_size = MAXALIGN(sizeof(varattrib));
Datum old_value;
Datum new_value;
/*
* Search for the biggest yet uncompressed internal attribute
*/
for (i = 0; i < numAttrs; i++)
{
if (toast_action[i] != ' ')
continue;
if (VARATT_IS_EXTENDED(toast_values[i]))
continue;
if (att[i]->attstorage != 'm')
continue;
if (toast_sizes[i] > biggest_size)
{
biggest_attno = i;
biggest_size = toast_sizes[i];
}
}
if (biggest_attno < 0)
break;
/*
* Attempt to compress it inline
*/
i = biggest_attno;
old_value = toast_values[i];
new_value = toast_compress_datum(old_value);
if (DatumGetPointer(new_value) != NULL)
{
/* successful compression */
if (toast_free[i])
pfree(DatumGetPointer(old_value));
toast_values[i] = new_value;
toast_free[i] = true;
toast_sizes[i] = VARATT_SIZE(toast_values[i]);
need_change = true;
need_free = true;
}
else
{
/*
* incompressible data, ignore on subsequent compression
* passes
*/
toast_action[i] = 'x';
}
}
/*
* Finally we store attributes of type 'm' external
*/
while (MAXALIGN(ComputeDataSize(tupleDesc, toast_values, toast_nulls)) >
maxDataLen && rel->rd_rel->reltoastrelid != InvalidOid)
{
int biggest_attno = -1;
int32 biggest_size = MAXALIGN(sizeof(varattrib));
Datum old_value;
/*--------
* Search for the biggest yet inlined attribute with
* attstorage = 'm'
*--------
*/
for (i = 0; i < numAttrs; i++)
{
if (toast_action[i] == 'p')
continue;
if (VARATT_IS_EXTERNAL(toast_values[i]))
continue;
if (att[i]->attstorage != 'm')
continue;
if (toast_sizes[i] > biggest_size)
{
biggest_attno = i;
biggest_size = toast_sizes[i];
}
}
if (biggest_attno < 0)
break;
/*
* Store this external
*/
i = biggest_attno;
old_value = toast_values[i];
toast_action[i] = 'p';
toast_values[i] = toast_save_datum(rel, toast_values[i]);
if (toast_free[i])
pfree(DatumGetPointer(old_value));
toast_free[i] = true;
toast_sizes[i] = VARATT_SIZE(toast_values[i]);
need_change = true;
need_free = true;
}
/*
* In the case we toasted any values, we need to build a new heap
* tuple with the changed values.
*/
if (need_change)
{
char *new_data;
int32 new_len;
MemoryContext oldcxt;
HeapTupleHeader olddata;
/*
* Calculate the new size of the tuple
*/
new_len = offsetof(HeapTupleHeaderData, t_bits);
if (has_nulls)
new_len += BITMAPLEN(numAttrs);
new_len = MAXALIGN(new_len);
new_len += ComputeDataSize(tupleDesc, toast_values, toast_nulls);
/*
* Remember the old memory location of the tuple (for below),
* switch to the memory context of the HeapTuple structure and
* allocate the new tuple.
*/
olddata = newtup->t_data;
oldcxt = MemoryContextSwitchTo(newtup->t_datamcxt);
new_data = palloc(new_len);
/*
* Put the tuple header and the changed values into place
*/
memcpy(new_data, newtup->t_data, newtup->t_data->t_hoff);
newtup->t_data = (HeapTupleHeader) new_data;
newtup->t_len = new_len;
DataFill((char *) (MAXALIGN((long) new_data +
offsetof(HeapTupleHeaderData, t_bits) +
((has_nulls) ? BITMAPLEN(numAttrs) : 0))),
tupleDesc,
toast_values,
toast_nulls,
&(newtup->t_data->t_infomask),
has_nulls ? newtup->t_data->t_bits : NULL);
/*
* In the case we modified a previously modified tuple again, free
* the memory from the previous run
*/
if ((char *) olddata != ((char *) newtup + HEAPTUPLESIZE))
pfree(olddata);
/*
* Switch back to the old memory context
*/
MemoryContextSwitchTo(oldcxt);
}
/*
* Free allocated temp values
*/
if (need_free)
for (i = 0; i < numAttrs; i++)
if (toast_free[i])
pfree(DatumGetPointer(toast_values[i]));
/*
* Delete external values from the old tuple
*/
if (need_delold)
for (i = 0; i < numAttrs; i++)
if (toast_delold[i])
toast_delete_datum(rel,
heap_getattr(oldtup, i + 1, tupleDesc, &old_isnull));
}
/* ----------
* toast_compress_datum -
*
* Create a compressed version of a varlena datum
*
* If we fail (ie, compressed result is actually bigger than original)
* then return NULL. We must not use compressed data if it'd expand
* the tuple!
* ----------
*/
Datum
toast_compress_datum(Datum value)
{
varattrib *tmp;
tmp = (varattrib *) palloc(sizeof(PGLZ_Header) + VARATT_SIZE(value));
pglz_compress(VARATT_DATA(value), VARATT_SIZE(value) - VARHDRSZ,
(PGLZ_Header *) tmp,
PGLZ_strategy_default);
if (VARATT_SIZE(tmp) < VARATT_SIZE(value))
{
/* successful compression */
VARATT_SIZEP(tmp) |= VARATT_FLAG_COMPRESSED;
return PointerGetDatum(tmp);
}
else
{
/* incompressible data */
pfree(tmp);
return PointerGetDatum(NULL);
}
}
/* ----------
* toast_save_datum -
*
* Save one single datum into the secondary relation and return
* a varattrib reference for it.
* ----------
*/
static Datum
toast_save_datum(Relation rel, Datum value)
{
Relation toastrel;
Relation toastidx;
HeapTuple toasttup;
InsertIndexResult idxres;
TupleDesc toasttupDesc;
Datum t_values[3];
char t_nulls[3];
varattrib *result;
struct
{
struct varlena hdr;
char data[TOAST_MAX_CHUNK_SIZE];
} chunk_data;
int32 chunk_size;
int32 chunk_seq = 0;
char *data_p;
int32 data_todo;
/*
* Create the varattrib reference
*/
result = (varattrib *) palloc(sizeof(varattrib));
result->va_header = sizeof(varattrib) | VARATT_FLAG_EXTERNAL;
if (VARATT_IS_COMPRESSED(value))
{
result->va_header |= VARATT_FLAG_COMPRESSED;
result->va_content.va_external.va_rawsize =
((varattrib *) value)->va_content.va_compressed.va_rawsize;
}
else
result->va_content.va_external.va_rawsize = VARATT_SIZE(value);
result->va_content.va_external.va_extsize =
VARATT_SIZE(value) - VARHDRSZ;
result->va_content.va_external.va_valueid = newoid();
result->va_content.va_external.va_toastrelid =
rel->rd_rel->reltoastrelid;
/*
* Initialize constant parts of the tuple data
*/
t_values[0] = ObjectIdGetDatum(result->va_content.va_external.va_valueid);
t_values[2] = PointerGetDatum(&chunk_data);
t_nulls[0] = ' ';
t_nulls[1] = ' ';
t_nulls[2] = ' ';
/*
* Get the data to process
*/
data_p = VARATT_DATA(value);
data_todo = VARATT_SIZE(value) - VARHDRSZ;
/*
* Open the toast relation
*/
toastrel = heap_open(rel->rd_rel->reltoastrelid, RowExclusiveLock);
toasttupDesc = toastrel->rd_att;
toastidx = index_open(toastrel->rd_rel->reltoastidxid);
/*
* Split up the item into chunks
*/
while (data_todo > 0)
{
/*
* Calculate the size of this chunk
*/
chunk_size = Min(TOAST_MAX_CHUNK_SIZE, data_todo);
/*
* Build a tuple and store it
*/
t_values[1] = Int32GetDatum(chunk_seq++);
VARATT_SIZEP(&chunk_data) = chunk_size + VARHDRSZ;
memcpy(VARATT_DATA(&chunk_data), data_p, chunk_size);
toasttup = heap_formtuple(toasttupDesc, t_values, t_nulls);
if (!HeapTupleIsValid(toasttup))
elog(ERROR, "Failed to build TOAST tuple");
heap_insert(toastrel, toasttup);
/*
* Create the index entry. We cheat a little here by not using
* FormIndexDatum: this relies on the knowledge that the index
* columns are the same as the initial columns of the table.
*
* Note also that there had better not be any user-created index on
* the TOAST table, since we don't bother to update anything else.
*/
idxres = index_insert(toastidx, t_values, t_nulls,
&(toasttup->t_self),
toastrel);
if (idxres == NULL)
elog(ERROR, "Failed to insert index entry for TOAST tuple");
/*
* Free memory
*/
pfree(idxres);
heap_freetuple(toasttup);
/*
* Move on to next chunk
*/
data_todo -= chunk_size;
data_p += chunk_size;
}
/*
* Done - close toast relation and return the reference
*/
index_close(toastidx);
heap_close(toastrel, RowExclusiveLock);
return PointerGetDatum(result);
}
/* ----------
* toast_delete_datum -
*
* Delete a single external stored value.
* ----------
*/
static void
toast_delete_datum(Relation rel, Datum value)
{
register varattrib *attr = (varattrib *) value;
Relation toastrel;
Relation toastidx;
ScanKeyData toastkey;
IndexScanDesc toastscan;
HeapTupleData toasttup;
RetrieveIndexResult indexRes;
Buffer buffer;
if (!VARATT_IS_EXTERNAL(attr))
return;
/*
* Open the toast relation and it's index
*/
toastrel = heap_open(attr->va_content.va_external.va_toastrelid,
RowExclusiveLock);
toastidx = index_open(toastrel->rd_rel->reltoastidxid);
/*
* Setup a scan key to fetch from the index by va_valueid (we don't
* particularly care whether we see them in sequence or not)
*/
ScanKeyEntryInitialize(&toastkey,
(bits16) 0,
(AttrNumber) 1,
(RegProcedure) F_OIDEQ,
ObjectIdGetDatum(attr->va_content.va_external.va_valueid));
/*
* Find the chunks by index
*/
toastscan = index_beginscan(toastidx, false, 1, &toastkey);
while ((indexRes = index_getnext(toastscan, ForwardScanDirection)) != NULL)
{
toasttup.t_self = indexRes->heap_iptr;
heap_fetch(toastrel, SnapshotToast, &toasttup, &buffer, toastscan);
pfree(indexRes);
if (!toasttup.t_data)
continue;
/*
* Have a chunk, delete it
*/
simple_heap_delete(toastrel, &toasttup.t_self);
ReleaseBuffer(buffer);
}
/*
* End scan and close relations
*/
index_endscan(toastscan);
index_close(toastidx);
heap_close(toastrel, RowExclusiveLock);
}
/* ----------
* toast_fetch_datum -
*
* Reconstruct an in memory varattrib from the chunks saved
* in the toast relation
* ----------
*/
static varattrib *
toast_fetch_datum(varattrib *attr)
{
Relation toastrel;
Relation toastidx;
ScanKeyData toastkey;
IndexScanDesc toastscan;
HeapTupleData toasttup;
HeapTuple ttup;
TupleDesc toasttupDesc;
RetrieveIndexResult indexRes;
Buffer buffer;
varattrib *result;
int32 ressize;
int32 residx,
nextidx;
int32 numchunks;
Pointer chunk;
bool isnull;
int32 chunksize;
ressize = attr->va_content.va_external.va_extsize;
numchunks = ((ressize - 1) / TOAST_MAX_CHUNK_SIZE) + 1;
result = (varattrib *) palloc(ressize + VARHDRSZ);
VARATT_SIZEP(result) = ressize + VARHDRSZ;
if (VARATT_IS_COMPRESSED(attr))
VARATT_SIZEP(result) |= VARATT_FLAG_COMPRESSED;
/*
* Open the toast relation and it's index
*/
toastrel = heap_open(attr->va_content.va_external.va_toastrelid,
AccessShareLock);
toasttupDesc = toastrel->rd_att;
toastidx = index_open(toastrel->rd_rel->reltoastidxid);
/*
* Setup a scan key to fetch from the index by va_valueid
*/
ScanKeyEntryInitialize(&toastkey,
(bits16) 0,
(AttrNumber) 1,
(RegProcedure) F_OIDEQ,
ObjectIdGetDatum(attr->va_content.va_external.va_valueid));
/*
* Read the chunks by index
*
* Note that because the index is actually on (valueid, chunkidx)
* we will see the chunks in chunkidx order, even though we didn't
* explicitly ask for it.
*/
nextidx = 0;
toastscan = index_beginscan(toastidx, false, 1, &toastkey);
while ((indexRes = index_getnext(toastscan, ForwardScanDirection)) != NULL)
{
toasttup.t_self = indexRes->heap_iptr;
heap_fetch(toastrel, SnapshotToast, &toasttup, &buffer, toastscan);
pfree(indexRes);
if (toasttup.t_data == NULL)
continue;
ttup = &toasttup;
/*
* Have a chunk, extract the sequence number and the data
*/
residx = DatumGetInt32(heap_getattr(ttup, 2, toasttupDesc, &isnull));
Assert(!isnull);
chunk = DatumGetPointer(heap_getattr(ttup, 3, toasttupDesc, &isnull));
Assert(!isnull);
chunksize = VARATT_SIZE(chunk) - VARHDRSZ;
/*
* Some checks on the data we've found
*/
if (residx != nextidx)
elog(ERROR, "unexpected chunk number %d (expected %d) for toast value %u",
residx, nextidx,
attr->va_content.va_external.va_valueid);
if (residx < numchunks - 1)
{
if (chunksize != TOAST_MAX_CHUNK_SIZE)
elog(ERROR, "unexpected chunk size %d in chunk %d for toast value %u",
chunksize, residx,
attr->va_content.va_external.va_valueid);
}
else if (residx < numchunks)
{
if ((residx * TOAST_MAX_CHUNK_SIZE + chunksize) != ressize)
elog(ERROR, "unexpected chunk size %d in chunk %d for toast value %u",
chunksize, residx,
attr->va_content.va_external.va_valueid);
}
else
elog(ERROR, "unexpected chunk number %d for toast value %u",
residx,
attr->va_content.va_external.va_valueid);
/*
* Copy the data into proper place in our result
*/
memcpy(((char *) VARATT_DATA(result)) + residx * TOAST_MAX_CHUNK_SIZE,
VARATT_DATA(chunk),
chunksize);
ReleaseBuffer(buffer);
nextidx++;
}
/*
* Final checks that we successfully fetched the datum
*/
if (nextidx != numchunks)
elog(ERROR, "missing chunk number %d for toast value %u",
nextidx,
attr->va_content.va_external.va_valueid);
/*
* End scan and close relations
*/
index_endscan(toastscan);
index_close(toastidx);
heap_close(toastrel, AccessShareLock);
return result;
}
#endif /* TUPLE_TOASTER_ACTIVE */
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