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Overview
| Comment: | Improved comments. No code changes. |
|---|---|
| Downloads: | Tarball | ZIP archive | SQL archive |
| Timelines: | family | ancestors | descendants | both | combine-disjuncts |
| Files: | files | file ages | folders |
| SHA1: |
23f71a26386ff2aff9800fe96cec1dc9 |
| User & Date: | drh 2015-03-16 13:12:34 |
Context
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2015-03-16
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| 17:48 | When the WHERE clause contains two OR-connected terms with identical operands but different operators, try to combine them into a single term. Example: (X=A OR X>A) becomes (X>=A). check-in: 8bdda827 user: drh tags: trunk | |
| 13:12 | Improved comments. No code changes. Closed-Leaf check-in: 23f71a26 user: drh tags: combine-disjuncts | |
| 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). check-in: 7a309768 user: drh tags: combine-disjuncts | |
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 OR-ed 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 two-way 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 OR-ed 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 |