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Overview
Comment:  Improved comments. No code changes. 

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Timelines:  family  ancestors  descendants  both  combinedisjuncts 
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SHA1:  23f71a26386ff2aff9800fe96cec1dc9 
User & Date:  drh 20150316 13:12:34 
Context
20150316
 
17:48  When the WHERE clause contains two ORconnected terms with identical operands but different operators, try to combine them into a single term. Example: (X=A OR X>A) becomes (X>=A). checkin: 8bdda827 user: drh tags: trunk  
13:12  Improved comments. No code changes. ClosedLeaf checkin: 23f71a26 user: drh tags: combinedisjuncts  
12:13  When a WHERE clause contains disjuncts with the same operands, try to combine them into a single operator. Example: (x=A OR x>A) becomes (x>=A). checkin: 7a309768 user: drh tags: combinedisjuncts  
Changes
Changes to src/where.c.
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/* ** Subterms pOne and pTwo are contained within WHERE clause pWC. The ** two subterms are in disjunction  they are ORed together. ** ** If these two terms are both of the form: "A op B" with the same ** A and B values but different operators and if the operators are ** compatible (if one is = and the other is <, for example) then ** add a new virtual term to pWC that is the combination of the ** two. ** ** Some examples: ** ** x<y OR x=y > x<=y ** x=y OR x=y > x=y ** x<=y OR x<y > x<=y ................................................................................ ** ** then create a new virtual term like this: ** ** x IN (expr1,expr2,expr3) ** ** CASE 2: ** ** If there is a twoway OR and one side has x>A and the other side ** has x=A (for the same x and A) then add a new virtual term to the ** WHERE clause of the form "x>=A". ** ** CASE 3: ** ** If all subterms are indexable by a single table T, then set ** ** WhereTerm.eOperator = WO_OR ** WhereTerm.u.pOrInfo>indexable = the cursor number for table T 




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/* ** Subterms pOne and pTwo are contained within WHERE clause pWC. The ** two subterms are in disjunction  they are ORed together. ** ** If these two terms are both of the form: "A op B" with the same ** A and B values but different operators and if the operators are ** compatible (if one is = and the other is <, for example) then ** add a new virtual AND term to pWC that is the combination of the ** two. ** ** Some examples: ** ** x<y OR x=y > x<=y ** x=y OR x=y > x=y ** x<=y OR x<y > x<=y ................................................................................ ** ** then create a new virtual term like this: ** ** x IN (expr1,expr2,expr3) ** ** CASE 2: ** ** If there are exactly two disjuncts one side has x>A and the other side ** has x=A (for the same x and A) then add a new virtual conjunct term to the ** WHERE clause of the form "x>=A". Example: ** ** x>A OR (x=A AND y>B) adds: x>=A ** ** The added conjunct can sometimes be helpful in query planning. ** ** CASE 3: ** ** If all subterms are indexable by a single table T, then set ** ** WhereTerm.eOperator = WO_OR ** WhereTerm.u.pOrInfo>indexable = the cursor number for table T 