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@ -664,7 +664,7 @@ options(<replaceable>relopts</replaceable> <type>local_relopts *</type>) returns |
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certain implementation-level heuristics will fail to identify and |
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certain implementation-level heuristics will fail to identify and |
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delete even one garbage index tuple (in which case a page split or |
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delete even one garbage index tuple (in which case a page split or |
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deduplication pass resolves the issue of an incoming new tuple not |
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deduplication pass resolves the issue of an incoming new tuple not |
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fitting on a leaf page). The worst case number of versions that |
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fitting on a leaf page). The worst-case number of versions that |
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any index scan must traverse (for any single logical row) is an |
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any index scan must traverse (for any single logical row) is an |
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important contributor to overall system responsiveness and |
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important contributor to overall system responsiveness and |
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throughput. A bottom-up index deletion pass targets suspected |
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throughput. A bottom-up index deletion pass targets suspected |
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@ -706,7 +706,7 @@ options(<replaceable>relopts</replaceable> <type>local_relopts *</type>) returns |
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This is expected with any B-Tree index that is subject to |
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This is expected with any B-Tree index that is subject to |
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significant version churn from <command>UPDATE</command>s that |
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significant version churn from <command>UPDATE</command>s that |
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rarely or never logically modify the columns that the index covers. |
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rarely or never logically modify the columns that the index covers. |
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The average and worst case number of versions per logical row can |
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The average and worst-case number of versions per logical row can |
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be kept low purely through targeted incremental deletion passes. |
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be kept low purely through targeted incremental deletion passes. |
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It's quite possible that the on-disk size of certain indexes will |
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It's quite possible that the on-disk size of certain indexes will |
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never increase by even one single page/block despite |
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never increase by even one single page/block despite |
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@ -811,7 +811,7 @@ options(<replaceable>relopts</replaceable> <type>local_relopts *</type>) returns |
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constraints) to use deduplication. This allows leaf pages to |
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constraints) to use deduplication. This allows leaf pages to |
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temporarily <quote>absorb</quote> extra version churn duplicates. |
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temporarily <quote>absorb</quote> extra version churn duplicates. |
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Deduplication in unique indexes augments bottom-up index deletion, |
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Deduplication in unique indexes augments bottom-up index deletion, |
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especially in cases where a long-running transactions holds a |
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especially in cases where a long-running transaction holds a |
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snapshot that blocks garbage collection. The goal is to buy time |
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snapshot that blocks garbage collection. The goal is to buy time |
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for the bottom-up index deletion strategy to become effective |
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for the bottom-up index deletion strategy to become effective |
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again. Delaying page splits until a single long-running |
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again. Delaying page splits until a single long-running |
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