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/*-------------------------------------------------------------------------
*
* ginlogic.c
* routines for performing binary- and ternary-logic consistent checks.
*
* A GIN operator class provides a consistent function which checks if a
* tuple matches a qual, when the given set of keys are present in the tuple.
* The consistent function is passed a TRUE/FALSE argument for every key,
* indicating if that key is present, and it returns TRUE or FALSE. However,
* a GIN scan can apply various optimizations, if it can determine that an
* item matches or doesn't match, even if it doesn't know if some of the keys
* are present or not. Hence, it's useful to have a ternary-logic consistent
* function, where each key can be TRUE (present), FALSE (not present),
* or MAYBE (don't know if present). This file provides such a ternary-logic
* consistent function, implemented by calling the regular boolean consistent
* function many times, with all the MAYBE arguments set to all combinations
* of TRUE and FALSE.
*
*
* Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* src/backend/access/gin/ginlogic.c
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/gin_private.h"
#include "access/reloptions.h"
#include "catalog/pg_collation.h"
#include "catalog/pg_type.h"
#include "miscadmin.h"
#include "storage/indexfsm.h"
#include "storage/lmgr.h"
/*
* Maximum number of MAYBE inputs that shimTriConsistentFn will try to
* resolve by calling all combinations.
*/
#define MAX_MAYBE_ENTRIES 4
/*
* A dummy consistent function for an EVERYTHING key. Just claim it matches.
*/
static bool
trueConsistentFn(GinScanKey key)
{
key->recheckCurItem = false;
return true;
}
static GinLogicValue
trueTriConsistentFn(GinScanKey key)
{
return GIN_MAYBE;
}
/*
* A helper function for calling a regular, binary logic, consistent function.
*/
static bool
directBoolConsistentFn(GinScanKey key)
{
/*
* Initialize recheckCurItem in case the consistentFn doesn't know it
* should set it. The safe assumption in that case is to force recheck.
*/
key->recheckCurItem = true;
return DatumGetBool(FunctionCall8Coll(key->consistentFmgrInfo,
key->collation,
PointerGetDatum(key->entryRes),
UInt16GetDatum(key->strategy),
key->query,
UInt32GetDatum(key->nuserentries),
PointerGetDatum(key->extra_data),
PointerGetDatum(&key->recheckCurItem),
PointerGetDatum(key->queryValues),
PointerGetDatum(key->queryCategories)));
}
/*
* A helper function for calling a native ternary logic consistent function.
*/
static GinLogicValue
directTriConsistentFn(GinScanKey key)
{
return DatumGetGinLogicValue(FunctionCall7Coll(key->triConsistentFmgrInfo,
key->collation,
PointerGetDatum(key->entryRes),
UInt16GetDatum(key->strategy),
key->query,
UInt32GetDatum(key->nuserentries),
PointerGetDatum(key->extra_data),
PointerGetDatum(key->queryValues),
PointerGetDatum(key->queryCategories)));
}
/*
* This function implements a binary logic consistency check, using a ternary
* logic consistent function provided by the opclass. GIN_MAYBE return value
* is interpreted as true with recheck flag.
*/
static bool
shimBoolConsistentFn(GinScanKey key)
{
GinLogicValue result;
result = DatumGetGinLogicValue(FunctionCall7Coll(key->triConsistentFmgrInfo,
key->collation,
PointerGetDatum(key->entryRes),
UInt16GetDatum(key->strategy),
key->query,
UInt32GetDatum(key->nuserentries),
PointerGetDatum(key->extra_data),
PointerGetDatum(key->queryValues),
PointerGetDatum(key->queryCategories)));
if (result == GIN_MAYBE)
{
key->recheckCurItem = true;
return true;
}
else
{
key->recheckCurItem = false;
return result;
}
}
/*
* This function implements a tri-state consistency check, using a boolean
* consistent function provided by the opclass.
*
* Our strategy is to call consistentFn with MAYBE inputs replaced with every
* combination of TRUE/FALSE. If consistentFn returns the same value for every
* combination, that's the overall result. Otherwise, return MAYBE. Testing
* every combination is O(n^2), so this is only feasible for a small number of
* MAYBE inputs.
*
* NB: This function modifies the key->entryRes array!
*/
static GinLogicValue
shimTriConsistentFn(GinScanKey key)
{
int nmaybe;
int maybeEntries[MAX_MAYBE_ENTRIES];
int i;
bool boolResult;
bool recheck = false;
GinLogicValue curResult;
/*
* Count how many MAYBE inputs there are, and store their indexes in
* maybeEntries. If there are too many MAYBE inputs, it's not feasible to
* test all combinations, so give up and return MAYBE.
*/
nmaybe = 0;
for (i = 0; i < key->nentries; i++)
{
if (key->entryRes[i] == GIN_MAYBE)
{
if (nmaybe >= MAX_MAYBE_ENTRIES)
return GIN_MAYBE;
maybeEntries[nmaybe++] = i;
}
}
/*
* If none of the inputs were MAYBE, so we can just call consistent
* function as is.
*/
if (nmaybe == 0)
return directBoolConsistentFn(key);
/* First call consistent function with all the maybe-inputs set FALSE */
for (i = 0; i < nmaybe; i++)
key->entryRes[maybeEntries[i]] = GIN_FALSE;
curResult = directBoolConsistentFn(key);
for (;;)
{
/* Twiddle the entries for next combination. */
for (i = 0; i < nmaybe; i++)
{
if (key->entryRes[maybeEntries[i]] == GIN_FALSE)
{
key->entryRes[maybeEntries[i]] = GIN_TRUE;
break;
}
else
key->entryRes[maybeEntries[i]] = GIN_FALSE;
}
if (i == nmaybe)
break;
boolResult = directBoolConsistentFn(key);
recheck |= key->recheckCurItem;
if (curResult != boolResult)
return GIN_MAYBE;
}
/* TRUE with recheck is taken to mean MAYBE */
if (curResult == GIN_TRUE && recheck)
curResult = GIN_MAYBE;
return curResult;
}
/*
* Set up the implementation of the consistent functions for a scan key.
*/
void
ginInitConsistentFunction(GinState *ginstate, GinScanKey key)
{
if (key->searchMode == GIN_SEARCH_MODE_EVERYTHING)
{
key->boolConsistentFn = trueConsistentFn;
key->triConsistentFn = trueTriConsistentFn;
}
else
{
key->consistentFmgrInfo = &ginstate->consistentFn[key->attnum - 1];
key->triConsistentFmgrInfo = &ginstate->triConsistentFn[key->attnum - 1];
key->collation = ginstate->supportCollation[key->attnum - 1];
if (OidIsValid(ginstate->consistentFn[key->attnum - 1].fn_oid))
key->boolConsistentFn = directBoolConsistentFn;
else
key->boolConsistentFn = shimBoolConsistentFn;
if (OidIsValid(ginstate->triConsistentFn[key->attnum - 1].fn_oid))
key->triConsistentFn = directTriConsistentFn;
else
key->triConsistentFn = shimTriConsistentFn;
}
}
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