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a933ee38bb
maintained for each cache entry. A cache entry will not be freed until the matching ReleaseSysCache call has been executed. This eliminates worries about cache entries getting dropped while still in use. See my posting to pg-hackers of even date for more info.
97 lines
3.5 KiB
C
97 lines
3.5 KiB
C
/*-------------------------------------------------------------------------
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*
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* hashjoin.h
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* internal structures for hash joins
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*
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*
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* Portions Copyright (c) 1996-2000, PostgreSQL, Inc
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $Id: hashjoin.h,v 1.20 2000/11/16 22:30:43 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef HASHJOIN_H
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#define HASHJOIN_H
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#include "access/htup.h"
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#include "storage/buffile.h"
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/* ----------------------------------------------------------------
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* hash-join hash table structures
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*
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* Each active hashjoin has a HashJoinTable control block which is
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* palloc'd in the executor's per-query context. All other storage needed
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* for the hashjoin is kept in private memory contexts, two for each hashjoin.
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* This makes it easy and fast to release the storage when we don't need it
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* anymore.
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*
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* The hashtable contexts are made children of the per-query context, ensuring
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* that they will be discarded at end of statement even if the join is
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* aborted early by an error. (Likewise, any temporary files we make will
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* be cleaned up by the virtual file manager in event of an error.)
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*
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* Storage that should live through the entire join is allocated from the
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* "hashCxt", while storage that is only wanted for the current batch is
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* allocated in the "batchCxt". By resetting the batchCxt at the end of
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* each batch, we free all the per-batch storage reliably and without tedium.
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* ----------------------------------------------------------------
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*/
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typedef struct HashJoinTupleData
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{
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struct HashJoinTupleData *next; /* link to next tuple in same
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* bucket */
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HeapTupleData htup; /* tuple header */
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} HashJoinTupleData;
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typedef HashJoinTupleData *HashJoinTuple;
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typedef struct HashTableData
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{
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int nbuckets; /* buckets in use during this batch */
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int totalbuckets; /* total number of (virtual) buckets */
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HashJoinTuple *buckets; /* buckets[i] is head of list of tuples */
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/* buckets array is per-batch storage, as are all the tuples */
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int nbatch; /* number of batches; 0 means 1-pass join */
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int curbatch; /* current batch #, or 0 during 1st pass */
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/*
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* all these arrays are allocated for the life of the hash join, but
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* only if nbatch > 0:
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*/
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BufFile **innerBatchFile; /* buffered virtual temp file per batch */
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BufFile **outerBatchFile; /* buffered virtual temp file per batch */
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long *outerBatchSize; /* count of tuples in each outer batch
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* file */
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long *innerBatchSize; /* count of tuples in each inner batch
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* file */
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/*
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* Info about the datatype being hashed. We assume that the inner
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* and outer sides of the hash are the same type, or at least
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* binary-compatible types.
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*/
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int16 typLen;
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bool typByVal;
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/*
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* During 1st scan of inner relation, we get tuples from executor. If
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* nbatch > 0 then tuples that don't belong in first nbuckets logical
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* buckets get dumped into inner-batch temp files. The same statements
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* apply for the 1st scan of the outer relation, except we write
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* tuples to outer-batch temp files. If nbatch > 0 then we do the
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* following for each batch: 1. Read tuples from inner batch file,
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* load into hash buckets. 2. Read tuples from outer batch file, match
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* to hash buckets and output.
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*/
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MemoryContext hashCxt; /* context for whole-hash-join storage */
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MemoryContext batchCxt; /* context for this-batch-only storage */
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} HashTableData;
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typedef HashTableData *HashJoinTable;
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#endif /* HASHJOIN_H */
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