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/*-------------------------------------------------------------------------
*
* hashjoin.h
* internal structures for hash joins
*
*
* Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $Id: hashjoin.h,v 1.23 2001/10/25 05:49:59 momjian Exp $
*
*-------------------------------------------------------------------------
*/
#ifndef HASHJOIN_H
#define HASHJOIN_H
#include "access/htup.h"
#include "storage/buffile.h"
/* ----------------------------------------------------------------
* hash-join hash table structures
*
* Each active hashjoin has a HashJoinTable control block which is
* palloc'd in the executor's per-query context. All other storage needed
* for the hashjoin is kept in private memory contexts, two for each hashjoin.
* This makes it easy and fast to release the storage when we don't need it
* anymore.
*
* The hashtable contexts are made children of the per-query context, ensuring
* that they will be discarded at end of statement even if the join is
* aborted early by an error. (Likewise, any temporary files we make will
* be cleaned up by the virtual file manager in event of an error.)
*
* Storage that should live through the entire join is allocated from the
* "hashCxt", while storage that is only wanted for the current batch is
* allocated in the "batchCxt". By resetting the batchCxt at the end of
* each batch, we free all the per-batch storage reliably and without tedium.
* ----------------------------------------------------------------
*/
typedef struct HashJoinTupleData
{
struct HashJoinTupleData *next; /* link to next tuple in same
* bucket */
HeapTupleData htup; /* tuple header */
} HashJoinTupleData;
typedef HashJoinTupleData *HashJoinTuple;
typedef struct HashTableData
{
int nbuckets; /* buckets in use during this batch */
int totalbuckets; /* total number of (virtual) buckets */
HashJoinTuple *buckets; /* buckets[i] is head of list of tuples */
/* buckets array is per-batch storage, as are all the tuples */
int nbatch; /* number of batches; 0 means 1-pass join */
int curbatch; /* current batch #, or 0 during 1st pass */
/*
* all these arrays are allocated for the life of the hash join, but
* only if nbatch > 0:
*/
BufFile **innerBatchFile; /* buffered virtual temp file per batch */
BufFile **outerBatchFile; /* buffered virtual temp file per batch */
long *outerBatchSize; /* count of tuples in each outer batch
* file */
long *innerBatchSize; /* count of tuples in each inner batch
* file */
/*
* Info about the datatype being hashed. We assume that the inner and
* outer sides of the hash are the same type, or at least
* binary-compatible types.
*/
int16 typLen;
bool typByVal;
/*
* During 1st scan of inner relation, we get tuples from executor. If
* nbatch > 0 then tuples that don't belong in first nbuckets logical
* buckets get dumped into inner-batch temp files. The same statements
* apply for the 1st scan of the outer relation, except we write
* tuples to outer-batch temp files. If nbatch > 0 then we do the
* following for each batch: 1. Read tuples from inner batch file,
* load into hash buckets. 2. Read tuples from outer batch file, match
* to hash buckets and output.
*/
MemoryContext hashCxt; /* context for whole-hash-join storage */
MemoryContext batchCxt; /* context for this-batch-only storage */
} HashTableData;
typedef HashTableData *HashJoinTable;
#endif /* HASHJOIN_H */
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