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Reduce size of two phase file header

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Previously 2PC header was fixed at 200 bytes, which in most cases wasted
WAL space for a workload using 2PC heavily.

Pavan Deolasee, reviewed by Petr Jelinek
This commit is contained in:
Simon Riggs 2016-03-10 12:51:46 +00:00
parent fcb4bfddb6
commit e0694cf9c7
1 changed files with 12 additions and 4 deletions
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16
src/backend/access/transam/twophase.c
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@ -126,6 +126,9 @@ int max_prepared_xacts = 0;
*
* typedef struct GlobalTransactionData *GlobalTransaction appears in
* twophase.h
*
* Note that the max value of GIDSIZE must fit in the uint16 gidlen,
* specified in TwoPhaseFileHeader.
*/
#define GIDSIZE 200
@ -851,7 +854,7 @@ TwoPhaseGetDummyProc(TransactionId xid)
/*
* Header for a 2PC state file
*/
#define TWOPHASE_MAGIC 0x57F94532 /* format identifier */
#define TWOPHASE_MAGIC 0x57F94533 /* format identifier */
typedef struct TwoPhaseFileHeader
{
@ -866,7 +869,7 @@ typedef struct TwoPhaseFileHeader
int32 nabortrels; /* number of delete-on-abort rels */
int32 ninvalmsgs; /* number of cache invalidation messages */
bool initfileinval; /* does relcache init file need invalidation? */
char gid[GIDSIZE]; /* GID for transaction */
uint16 gidlen; /* length of the GID - GID follows the header */
} TwoPhaseFileHeader;
/*
@ -977,9 +980,10 @@ StartPrepare(GlobalTransaction gxact)
hdr.nabortrels = smgrGetPendingDeletes(false, &abortrels);
hdr.ninvalmsgs = xactGetCommittedInvalidationMessages(&invalmsgs,
&hdr.initfileinval);
StrNCpy(hdr.gid, gxact->gid, GIDSIZE);
hdr.gidlen = strlen(gxact->gid) + 1; /* Include '\0' */
save_state_data(&hdr, sizeof(TwoPhaseFileHeader));
save_state_data(gxact->gid, hdr.gidlen);
/*
* Add the additional info about subxacts, deletable files and cache
@ -1360,6 +1364,7 @@ FinishPreparedTransaction(const char *gid, bool isCommit)
hdr = (TwoPhaseFileHeader *) buf;
Assert(TransactionIdEquals(hdr->xid, xid));
bufptr = buf + MAXALIGN(sizeof(TwoPhaseFileHeader));
bufptr += MAXALIGN(hdr->gidlen);
children = (TransactionId *) bufptr;
bufptr += MAXALIGN(hdr->nsubxacts * sizeof(TransactionId));
commitrels = (RelFileNode *) bufptr;
@ -1915,6 +1920,7 @@ RecoverPreparedTransactions(void)
TwoPhaseFileHeader *hdr;
TransactionId *subxids;
GlobalTransaction gxact;
const char *gid;
int i;
xid = (TransactionId) strtoul(clde->d_name, NULL, 16);
@ -1947,6 +1953,8 @@ RecoverPreparedTransactions(void)
hdr = (TwoPhaseFileHeader *) buf;
Assert(TransactionIdEquals(hdr->xid, xid));
bufptr = buf + MAXALIGN(sizeof(TwoPhaseFileHeader));
gid = (const char *) bufptr;
bufptr += MAXALIGN(hdr->gidlen);
subxids = (TransactionId *) bufptr;
bufptr += MAXALIGN(hdr->nsubxacts * sizeof(TransactionId));
bufptr += MAXALIGN(hdr->ncommitrels * sizeof(RelFileNode));
@ -1975,7 +1983,7 @@ RecoverPreparedTransactions(void)
/*
* Recreate its GXACT and dummy PGPROC
*/
gxact = MarkAsPreparing(xid, hdr->gid,
gxact = MarkAsPreparing(xid, gid,
hdr->prepared_at,
hdr->owner, hdr->database);
gxact->ondisk = true;