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Avoid O(N^2) behavior when enlarging SPI tuple table in spi_printtup().

For no obvious reason, spi_printtup() was coded to enlarge the tuplepointer table by just 256 slots at a time, rather than doubling the size ateach reallocation, as is our usual habit. For very large SPI results, thismakes for O(N^2) time spent in repalloc(), which of course soon comes todominate the runtime. Use the standard doubling approach instead.This is a longstanding performance bug, so back-patch to all activebranches.Neil Conway

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src/backend/executor
- spi.c

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`‎src/backend/executor/spi.c`

Lines changed: 2 additions & 1 deletion

Original file line number	Diff line number	Diff line change
`@@ -1797,7 +1797,8 @@ spi_printtup(TupleTableSlot slot, DestReceiver self)`
`1797`	`1797`
`1798`	`1798`	`if (tuptable->free==0)`
`1799`	`1799`	`{`
`1800`		`-tuptable->free=256;`
	`1800`	`+/* Double the size of the pointer array */`
	`1801`	`+tuptable->free=tuptable->alloced;`
`1801`	`1802`	`tuptable->alloced+=tuptable->free;`
`1802`	`1803`	`tuptable->vals= (HeapTuple*)repalloc(tuptable->vals,`
`1803`	`1804`	`tuptable->alloced*sizeof(HeapTuple));`

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Commit68a14ca

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`‎src/backend/executor/spi.c`

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