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Fix typos in comments

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Dmitriy Olshevskiy
This commit is contained in:
Magnus Hagander
2015-05-17 14:57:30 +02:00
parent 6b665454e3
commit 3b075e9d7b
12 changed files with 19 additions and 19 deletions
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14
src/backend/access/gin/ginpostinglist.c
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@ -23,7 +23,7 @@
/*
* For encoding purposes, item pointers are represented as 64-bit unsigned
* integers. The lowest 11 bits represent the offset number, and the next
* lowest 32 bits are the block number. That leaves 17 bits unused, ie.
* lowest 32 bits are the block number. That leaves 17 bits unused, i.e.
* only 43 low bits are used.
*
* These 43-bit integers are encoded using varbyte encoding. In each byte,
@ -51,16 +51,16 @@
* Removing number is actually replacement of two numbers with their sum. We
* have to prove that varbyte encoding of a sum can't be longer than varbyte
* encoding of its summands. Sum of two numbers is at most one bit wider than
* than the larger of the summands. Widening a number by one bit enlarges its
* length in varbyte encoding by at most one byte. Therefore, varbyte encoding
* of sum is at most one byte longer than varbyte encoding of larger summand.
* Lesser summand is at least one byte, so the sum cannot take more space than
* the summands, Q.E.D.
* the larger of the summands. Widening a number by one bit enlarges its length
* in varbyte encoding by at most one byte. Therefore, varbyte encoding of sum
* is at most one byte longer than varbyte encoding of larger summand. Lesser
* summand is at least one byte, so the sum cannot take more space than the
* summands, Q.E.D.
*
* This property greatly simplifies VACUUM, which can assume that posting
* lists always fit on the same page after vacuuming. Note that even though
* that holds for removing items from a posting list, you must also be
* careful to not cause expansion e.g when merging uncompressed items on the
* careful to not cause expansion e.g. when merging uncompressed items on the
* page into the compressed lists, when vacuuming.
*/