Comparing Distributed Indexing To Mapreduce or Not?

Comparing Distributed Indexing: To Mapreduce or Not? Richard McCreadie Craig Macdonald Iadh Ounis

Talk Outline ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

MOTIVATIONS ,[object Object],[object Object]

Why is Efficient Indexing Important? ,[object Object],[object Object],[object Object],Collection Data Year Docs Size(GB) WT2G Web 1999 240k 2.0 GOV Web 2002 1.8M 18.0 Blogs06 Blogs 2006 3M 13.0 GOV2 Web 2004 25M 425.0 ClueWeb09 Web 2009 1.2B 25,000

[object Object],[object Object],[object Object],Solutions? MapReduce

Contributions ,[object Object],[object Object],[object Object],[object Object],[object Object]

CLASSICAL INDEXING ,[object Object],[object Object],[object Object]

Classical Indexing ,[object Object],[object Object],[object Object],[object Object],(I.H. Witten, A. Moffat and T.C. Bell, 1999) Lexicon Posting List term Total docs Total frequency pointer Document number frequency

[object Object],[object Object],[object Object],Single-Pass In-Memory Indexing <> <> <> <> <> <> DISK Compressed Files % Used RAM t1 t2 t3 Indexer Final Inverted Index

How can Indexing be Distributed? ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Problems with Classical Approaches ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

MAPREDUCE INDEXING ,[object Object],[object Object]

MapReduce ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Indexing with MapReduce ,[object Object],[object Object],[object Object],[object Object],Dean & Ghemawat, MapReduce: Simplified data processing on large clusters. OSDI 2004 Emit each word in the document A big intermediate sort Lots of merging Approach Emits Sorting Num emits per map Emit size D&G_Token Tokens Lots Lots Tiny D&G_Term Terms Lots Many Tiny Nutch Documents Little Some Average Single-Pass Posting lists Some Few Large

D&G_Token & D&G_Term ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Emit every token Emit every term

Nutch Style Indexing ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Emit every document

Our Single-Pass Indexing Strategy ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Emit limited Posting-Lists

Our MapReduce Indexing Strategy (2) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

EXPERIMENTATION & RESULTS ,[object Object],[object Object]

Research Questions ,[object Object],[object Object],[object Object],[object Object]

Evaluation of MapReduce Indexing ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Experimental Setup ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Target Indexing Throughput Table 1 : Throughput (MB/sec) when indexing .GOV2 with m machines ,[object Object],[object Object],Indexing Strategy 1 2 4 6 8 Shared-Nothing Distributed 3 6 12 18 24 Shared-Corpus Distributed MapReduce D&G_Token MapReduce D&G_Term MapReduce Single-Pass Number of Machines Allocated

Baseline Indexing Throughput ,[object Object],[object Object],[object Object],[object Object],Table 1 : Throughput (MB/sec) when indexing .GOV2 with m machines Indexing Strategy 1 2 4 6 8 Shared-Nothing Distributed 3 6 12 18 24 Shared-Corpus Distributed 2.44 4.6 12.8 12.4 12.8 MapReduce D&G_Token MapReduce D&G_Term MapReduce Single-Pass Number of Machines Allocated

D&G_Token Indexing Throughput ,[object Object],[object Object],Table 1 : Throughput (MB/sec) when indexing .GOV2 with m machines Indexing Strategy 1 2 4 6 8 Shared-Nothing Distributed 3 6 12 18 24 Shared-Corpus Distributed 2.44 4.6 12.8 12.4 12.8 MapReduce D&G_Token - - - - - MapReduce D&G_Term MapReduce Single-Pass Number of Machines Allocated

D&G_Term Indexing Throughput ,[object Object],[object Object],[object Object],[object Object],Table 1 : Throughput (MB/sec) when indexing .GOV2 with m machines Indexing Strategy 1 2 4 6 8 Shared-Nothing Distributed 3 6 12 18 24 Shared-Corpus Distributed 2.44 4.6 12.8 12.4 12.8 MapReduce D&G_Token - - - - - MapReduce D&G_Term 1.15 1.59 4.01 4.71 6.38 MapReduce Single-Pass Number of Machines Allocated

Single-Pass Indexing Throughput ,[object Object],[object Object],[object Object],Table 1 : Throughput (MB/sec) when indexing .GOV2 with m machines Indexing Strategy 1 2 4 6 8 Shared-Nothing Distributed 3 6 12 18 24 Shared-Corpus Distributed 2.44 4.6 12.8 12.4 12.8 MapReduce D&G_Token - - - - - MapReduce D&G_Term 1.15 1.59 4.01 4.71 6.38 MapReduce Single-Pass 2.59 5.19 9.45 13.16 17.31 Number of Machines Allocated

Conclusions ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Comparing Distributed Indexing To Mapreduce or Not?

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