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pg_stat_statements: Widen query IDs from 32 bits to 64 bits.

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This takes advantage of the infrastructure introduced by commit
81c5e46c49 to greatly reduce the
likelihood that two different queries will end up with the same query
ID.  It's still possible, of course, but whereas before it the chances
of a collision reached 25% around 50,000 queries, it will now take
more than 3 billion queries.

Backward incompatibility: Because the type exposed at the SQL level is
int8, users may now see negative query IDs in the pg_stat_statements
view (and also, query IDs more than 4 billion, which was the old
limit).

Patch by me, reviewed by Michael Paquier and Peter Geoghegan.

Discussion: http://postgr.es/m/CA+TgmobG_Kp4cBKFmsznUAaM1GWW6hhRNiZC0KjRMOOeYnz5Yw@mail.gmail.com
This commit is contained in:
Robert Haas
2017-10-11 19:52:46 -04:00
parent f2dec34e19
commit cff440d368
7 changed files with 42 additions and 60 deletions
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7
src/backend/nodes/outfuncs.c
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@ -54,6 +54,11 @@ static void outChar(StringInfo str, char c);
#define WRITE_UINT_FIELD(fldname) \
appendStringInfo(str, " :" CppAsString(fldname) " %u", node->fldname)
/* Write an unsigned integer field (anything written with UINT64_FORMAT) */
#define WRITE_UINT64_FIELD(fldname) \
appendStringInfo(str, " :" CppAsString(fldname) " " UINT64_FORMAT, \
node->fldname)
/* Write an OID field (don't hard-wire assumption that OID is same as uint) */
#define WRITE_OID_FIELD(fldname) \
appendStringInfo(str, " :" CppAsString(fldname) " %u", node->fldname)
@ -260,7 +265,7 @@ _outPlannedStmt(StringInfo str, const PlannedStmt *node)
WRITE_NODE_TYPE("PLANNEDSTMT");
WRITE_ENUM_FIELD(commandType, CmdType);
WRITE_UINT_FIELD(queryId);
WRITE_UINT64_FIELD(queryId);
WRITE_BOOL_FIELD(hasReturning);
WRITE_BOOL_FIELD(hasModifyingCTE);
WRITE_BOOL_FIELD(canSetTag);