greenplumn indextuple 源码
greenplumn indextuple 代码
文件路径：/src/backend/access/common/indextuple.c
/*-------------------------------------------------------------------------
*
* indextuple.c
* This file contains index tuple accessor and mutator routines,
* as well as various tuple utilities.
*
* Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* src/backend/access/common/indextuple.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/htup_details.h"
#include "access/itup.h"
#include "access/tuptoaster.h"
/* ----------------------------------------------------------------
* index_ tuple interface routines
* ----------------------------------------------------------------
*/
/* ----------------
* index_form_tuple
*
* This shouldn't leak any memory; otherwise, callers such as
* tuplesort_putindextuplevalues() will be very unhappy.
*
* This shouldn't perform external table access provided caller
* does not pass values that are stored EXTERNAL.
* ----------------
*/
IndexTuple
index_form_tuple(TupleDesc tupleDescriptor,
Datum *values,
bool *isnull)
{
char *tp; /* tuple pointer */
IndexTuple tuple; /* return tuple */
Size size,
data_size,
hoff;
int i;
unsigned short infomask = 0;
bool hasnull = false;
uint16 tupmask = 0;
int numberOfAttributes = tupleDescriptor->natts;
#ifdef TOAST_INDEX_HACK
Datum untoasted_values[INDEX_MAX_KEYS];
bool untoasted_free[INDEX_MAX_KEYS];
#endif
if (numberOfAttributes > INDEX_MAX_KEYS)
ereport(ERROR,
(errcode(ERRCODE_TOO_MANY_COLUMNS),
errmsg("number of index columns (%d) exceeds limit (%d)",
numberOfAttributes, INDEX_MAX_KEYS)));
#ifdef TOAST_INDEX_HACK
for (i = 0; i < numberOfAttributes; i++)
{
Form_pg_attribute att = TupleDescAttr(tupleDescriptor, i);
untoasted_values[i] = values[i];
untoasted_free[i] = false;
/* Do nothing if value is NULL or not of varlena type */
if (isnull[i] || att->attlen != -1)
continue;
/*
* If value is stored EXTERNAL, must fetch it so we are not depending
* on outside storage. This should be improved someday.
*/
if (VARATT_IS_EXTERNAL(DatumGetPointer(values[i])))
{
untoasted_values[i] =
PointerGetDatum(heap_tuple_fetch_attr((struct varlena *)
DatumGetPointer(values[i])));
untoasted_free[i] = true;
}
/*
* If value is above size target, and is of a compressible datatype,
* try to compress it in-line.
*/
if (!VARATT_IS_EXTENDED(DatumGetPointer(untoasted_values[i])) &&
VARSIZE(DatumGetPointer(untoasted_values[i])) > TOAST_INDEX_TARGET &&
(att->attstorage == 'x' || att->attstorage == 'm'))
{
Datum cvalue = toast_compress_datum(untoasted_values[i]);
if (DatumGetPointer(cvalue) != NULL)
{
/* successful compression */
if (untoasted_free[i])
pfree(DatumGetPointer(untoasted_values[i]));
untoasted_values[i] = cvalue;
untoasted_free[i] = true;
}
}
}
#endif
for (i = 0; i < numberOfAttributes; i++)
{
if (isnull[i])
{
hasnull = true;
break;
}
}
if (hasnull)
infomask |= INDEX_NULL_MASK;
hoff = IndexInfoFindDataOffset(infomask);
#ifdef TOAST_INDEX_HACK
data_size = heap_compute_data_size(tupleDescriptor,
untoasted_values, isnull);
#else
data_size = heap_compute_data_size(tupleDescriptor,
values, isnull);
#endif
size = hoff + data_size;
size = MAXALIGN(size); /* be conservative */
tp = (char *) palloc0(size);
tuple = (IndexTuple) tp;
heap_fill_tuple(tupleDescriptor,
#ifdef TOAST_INDEX_HACK
untoasted_values,
#else
values,
#endif
isnull,
(char *) tp + hoff,
data_size,
&tupmask,
(hasnull ? (bits8 *) tp + sizeof(IndexTupleData) : NULL));
#ifdef TOAST_INDEX_HACK
for (i = 0; i < numberOfAttributes; i++)
{
if (untoasted_free[i])
pfree(DatumGetPointer(untoasted_values[i]));
}
#endif
/*
* We do this because heap_fill_tuple wants to initialize a "tupmask"
* which is used for HeapTuples, but we want an indextuple infomask. The
* only relevant info is the "has variable attributes" field. We have
* already set the hasnull bit above.
*/
if (tupmask & HEAP_HASVARWIDTH)
infomask |= INDEX_VAR_MASK;
/* Also assert we got rid of external attributes */
#ifdef TOAST_INDEX_HACK
Assert((tupmask & HEAP_HASEXTERNAL) == 0);
#endif
/*
* Here we make sure that the size will fit in the field reserved for it
* in t_info.
*/
if ((size & INDEX_SIZE_MASK) != size)
ereport(ERROR,
(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
errmsg("index row requires %zu bytes, maximum size is %zu",
size, (Size) INDEX_SIZE_MASK)));
infomask |= size;
/*
* initialize metadata
*/
tuple->t_info = infomask;
return tuple;
}
/* ----------------
* nocache_index_getattr
*
* This gets called from index_getattr() macro, and only in cases
* where we can't use cacheoffset and the value is not null.
*
* This caches attribute offsets in the attribute descriptor.
*
* An alternative way to speed things up would be to cache offsets
* with the tuple, but that seems more difficult unless you take
* the storage hit of actually putting those offsets into the
* tuple you send to disk. Yuck.
*
* This scheme will be slightly slower than that, but should
* perform well for queries which hit large #'s of tuples. After
* you cache the offsets once, examining all the other tuples using
* the same attribute descriptor will go much quicker. -cim 5/4/91
* ----------------
*/
Datum
nocache_index_getattr(IndexTuple tup,
int attnum,
TupleDesc tupleDesc)
{
char *tp; /* ptr to data part of tuple */
bits8 *bp = NULL; /* ptr to null bitmap in tuple */
bool slow = false; /* do we have to walk attrs? */
int data_off; /* tuple data offset */
int off; /* current offset within data */
/* ----------------
* Three cases:
*
* 1: No nulls and no variable-width attributes.
* 2: Has a null or a var-width AFTER att.
* 3: Has nulls or var-widths BEFORE att.
* ----------------
*/
data_off = IndexInfoFindDataOffset(tup->t_info);
attnum--;
if (IndexTupleHasNulls(tup))
{
/*
* there's a null somewhere in the tuple
*
* check to see if desired att is null
*/
/* XXX "knows" t_bits are just after fixed tuple header! */
bp = (bits8 *) ((char *) tup + sizeof(IndexTupleData));
/*
* Now check to see if any preceding bits are null...
*/
{
int byte = attnum >> 3;
int finalbit = attnum & 0x07;
/* check for nulls "before" final bit of last byte */
if ((~bp[byte]) & ((1 << finalbit) - 1))
slow = true;
else
{
/* check for nulls in any "earlier" bytes */
int i;
for (i = 0; i < byte; i++)
{
if (bp[i] != 0xFF)
{
slow = true;
break;
}
}
}
}
}
tp = (char *) tup + data_off;
if (!slow)
{
Form_pg_attribute att;
/*
* If we get here, there are no nulls up to and including the target
* attribute. If we have a cached offset, we can use it.
*/
att = TupleDescAttr(tupleDesc, attnum);
if (att->attcacheoff >= 0)
return fetchatt(att, tp + att->attcacheoff);
/*
* Otherwise, check for non-fixed-length attrs up to and including
* target. If there aren't any, it's safe to cheaply initialize the
* cached offsets for these attrs.
*/
if (IndexTupleHasVarwidths(tup))
{
int j;
for (j = 0; j <= attnum; j++)
{
if (TupleDescAttr(tupleDesc, j)->attlen <= 0)
{
slow = true;
break;
}
}
}
}
if (!slow)
{
int natts = tupleDesc->natts;
int j = 1;
/*
* If we get here, we have a tuple with no nulls or var-widths up to
* and including the target attribute, so we can use the cached offset
* ... only we don't have it yet, or we'd not have got here. Since
* it's cheap to compute offsets for fixed-width columns, we take the
* opportunity to initialize the cached offsets for *all* the leading
* fixed-width columns, in hope of avoiding future visits to this
* routine.
*/
TupleDescAttr(tupleDesc, 0)->attcacheoff = 0;
/* we might have set some offsets in the slow path previously */
while (j < natts && TupleDescAttr(tupleDesc, j)->attcacheoff > 0)
j++;
off = TupleDescAttr(tupleDesc, j - 1)->attcacheoff +
TupleDescAttr(tupleDesc, j - 1)->attlen;
for (; j < natts; j++)
{
Form_pg_attribute att = TupleDescAttr(tupleDesc, j);
if (att->attlen <= 0)
break;
off = att_align_nominal(off, att->attalign);
att->attcacheoff = off;
off += att->attlen;
}
Assert(j > attnum);
off = TupleDescAttr(tupleDesc, attnum)->attcacheoff;
}
else
{
bool usecache = true;
int i;
/*
* Now we know that we have to walk the tuple CAREFULLY. But we still
* might be able to cache some offsets for next time.
*
* Note - This loop is a little tricky. For each non-null attribute,
* we have to first account for alignment padding before the attr,
* then advance over the attr based on its length. Nulls have no
* storage and no alignment padding either. We can use/set
* attcacheoff until we reach either a null or a var-width attribute.
*/
off = 0;
for (i = 0;; i++) /* loop exit is at "break" */
{
Form_pg_attribute att = TupleDescAttr(tupleDesc, i);
if (IndexTupleHasNulls(tup) && att_isnull(i, bp))
{
usecache = false;
continue; /* this cannot be the target att */
}
/* If we know the next offset, we can skip the rest */
if (usecache && att->attcacheoff >= 0)
off = att->attcacheoff;
else if (att->attlen == -1)
{
/*
* We can only cache the offset for a varlena attribute if the
* offset is already suitably aligned, so that there would be
* no pad bytes in any case: then the offset will be valid for
* either an aligned or unaligned value.
*/
if (usecache &&
off == att_align_nominal(off, att->attalign))
att->attcacheoff = off;
else
{
off = att_align_pointer(off, att->attalign, -1,
tp + off);
usecache = false;
}
}
else
{
/* not varlena, so safe to use att_align_nominal */
off = att_align_nominal(off, att->attalign);
if (usecache)
att->attcacheoff = off;
}
if (i == attnum)
break;
off = att_addlength_pointer(off, att->attlen, tp + off);
if (usecache && att->attlen <= 0)
usecache = false;
}
}
return fetchatt(TupleDescAttr(tupleDesc, attnum), tp + off);
}
/*
* Convert an index tuple into Datum/isnull arrays.
*
* The caller must allocate sufficient storage for the output arrays.
* (INDEX_MAX_KEYS entries should be enough.)
*
* This is nearly the same as heap_deform_tuple(), but for IndexTuples.
* One difference is that the tuple should never have any missing columns.
*/
void
index_deform_tuple(IndexTuple tup, TupleDesc tupleDescriptor,
Datum *values, bool *isnull)
{
int hasnulls = IndexTupleHasNulls(tup);
int natts = tupleDescriptor->natts; /* number of atts to extract */
int attnum;
char *tp; /* ptr to tuple data */
int off; /* offset in tuple data */
bits8 *bp; /* ptr to null bitmap in tuple */
bool slow = false; /* can we use/set attcacheoff? */
/* Assert to protect callers who allocate fixed-size arrays */
Assert(natts <= INDEX_MAX_KEYS);
/* XXX "knows" t_bits are just after fixed tuple header! */
bp = (bits8 *) ((char *) tup + sizeof(IndexTupleData));
tp = (char *) tup + IndexInfoFindDataOffset(tup->t_info);
off = 0;
for (attnum = 0; attnum < natts; attnum++)
{
Form_pg_attribute thisatt = TupleDescAttr(tupleDescriptor, attnum);
if (hasnulls && att_isnull(attnum, bp))
{
values[attnum] = (Datum) 0;
isnull[attnum] = true;
slow = true; /* can't use attcacheoff anymore */
continue;
}
isnull[attnum] = false;
if (!slow && thisatt->attcacheoff >= 0)
off = thisatt->attcacheoff;
else if (thisatt->attlen == -1)
{
/*
* We can only cache the offset for a varlena attribute if the
* offset is already suitably aligned, so that there would be no
* pad bytes in any case: then the offset will be valid for either
* an aligned or unaligned value.
*/
if (!slow &&
off == att_align_nominal(off, thisatt->attalign))
thisatt->attcacheoff = off;
else
{
off = att_align_pointer(off, thisatt->attalign, -1,
tp + off);
slow = true;
}
}
else
{
/* not varlena, so safe to use att_align_nominal */
off = att_align_nominal(off, thisatt->attalign);
if (!slow)
thisatt->attcacheoff = off;
}
values[attnum] = fetchatt(thisatt, tp + off);
off = att_addlength_pointer(off, thisatt->attlen, tp + off);
if (thisatt->attlen <= 0)
slow = true; /* can't use attcacheoff anymore */
}
}
/*
* Create a palloc'd copy of an index tuple.
*/
IndexTuple
CopyIndexTuple(IndexTuple source)
{
IndexTuple result;
Size size;
size = IndexTupleSize(source);
result = (IndexTuple) palloc(size);
memcpy(result, source, size);
return result;
}
/*
* Create a palloc'd copy of an index tuple, leaving only the first
* leavenatts attributes remaining.
*
* Truncation is guaranteed to result in an index tuple that is no
* larger than the original. It is safe to use the IndexTuple with
* the original tuple descriptor, but caller must avoid actually
* accessing truncated attributes from returned tuple! In practice
* this means that index_getattr() must be called with special care,
* and that the truncated tuple should only ever be accessed by code
* under caller's direct control.
*
* It's safe to call this function with a buffer lock held, since it
* never performs external table access. If it ever became possible
* for index tuples to contain EXTERNAL TOAST values, then this would
* have to be revisited.
*/
IndexTuple
index_truncate_tuple(TupleDesc sourceDescriptor, IndexTuple source,
int leavenatts)
{
TupleDesc truncdesc;
Datum values[INDEX_MAX_KEYS];
bool isnull[INDEX_MAX_KEYS];
IndexTuple truncated;
Assert(leavenatts <= sourceDescriptor->natts);
/* Easy case: no truncation actually required */
if (leavenatts == sourceDescriptor->natts)
return CopyIndexTuple(source);
/* Create temporary descriptor to scribble on */
truncdesc = palloc(TupleDescSize(sourceDescriptor));
TupleDescCopy(truncdesc, sourceDescriptor);
truncdesc->natts = leavenatts;
/* Deform, form copy of tuple with fewer attributes */
index_deform_tuple(source, truncdesc, values, isnull);
truncated = index_form_tuple(truncdesc, values, isnull);
truncated->t_tid = source->t_tid;
Assert(IndexTupleSize(truncated) <= IndexTupleSize(source));
/*
* Cannot leak memory here, TupleDescCopy() doesn't allocate any inner
* structure, so, plain pfree() should clean all allocated memory
*/
pfree(truncdesc);
return truncated;
}
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