我有一个名为street_names的表格：
CREATE TABLE street_names (
id INTEGER PRIMARY KEY NOT NULL,
name TEXT UNIQUE NOT NULL
);
使用LIKE搜索时，它会使用索引并立即返回结果。但是，请采用这个更大的表达式：
SELECT sn.name, sa.house_number, sa.entrance, pc.postal_code, ci.name, mu.name,
co.name, sa.latitude, sa.longitude
FROM
street_addresses AS sa
INNER JOIN street_names AS sn ON sa.street_name = sn.id
INNER JOIN postal_codes AS pc ON sa.postal_code = pc.id
INNER JOIN cities AS ci ON sa.city = ci.id
INNER JOIN municipalities AS mu ON sa.municipality = mu.id
INNER JOIN counties AS co ON mu.county = co.id
WHERE
sn.name = "FORNEBUVEIEN" AND
sa.house_number = 13
ORDER BY ci.name ASC, sn.name ASC, sa.house_number ASC, sa.entrance ASC
LIMIT 0, 100;
在当前状态下，它的闪电速度非常快，并且可以在我的机器上每秒运行6000次，但只要我将街道名称上的=更改为LIKE：< / p>
SELECT sn.name, sa.house_number, sa.entrance, pc.postal_code, ci.name, mu.name,
co.name, sa.latitude, sa.longitude
FROM
street_addresses AS sa
INNER JOIN street_names AS sn ON sa.street_name = sn.id
INNER JOIN postal_codes AS pc ON sa.postal_code = pc.id
INNER JOIN cities AS ci ON sa.city = ci.id
INNER JOIN municipalities AS mu ON sa.municipality = mu.id
INNER JOIN counties AS co ON mu.county = co.id
WHERE
sn.name LIKE "FORNEBUVEIEN" AND
sa.house_number = 13
ORDER BY ci.name ASC, sn.name ASC, sa.house_number ASC, sa.entrance ASC
LIMIT 0, 100;
它变坏了，在我的机器上每秒运行10次。为什么是这样？我所做的唯一更改是将索引列上的=更改为LIKE，并且查询甚至不包含任何通配符。
表模式：
CREATE TABLE street_addresses (
id INTEGER PRIMARY KEY NOT NULL,
house_number INTEGER NOT NULL,
entrance TEXT NOT NULL,
latitude REAL NOT NULL,
longitude REAL NOT NULL,
street_name INTEGER NOT NULL REFERENCES street_names(id),
postal_code INTEGER NOT NULL REFERENCES postal_codes(id),
city INTEGER NOT NULL REFERENCES cities(id),
municipality INTEGER NOT NULL REFERENCES municipalities(id),
CONSTRAINT unique_address UNIQUE(
street_name, house_number, entrance, postal_code, city
)
);
CREATE TABLE street_names (
id INTEGER PRIMARY KEY NOT NULL,
name TEXT UNIQUE NOT NULL
);
CREATE TABLE postal_codes (
id INTEGER PRIMARY KEY NOT NULL,
postal_code INTEGER NOT NULL,
city INTEGER NOT NULL REFERENCES cities(id),
CONSTRAINT unique_postal_code UNIQUE(postal_code, city)
);
CREATE TABLE cities (
id INTEGER PRIMARY KEY NOT NULL,
name TEXT NOT NULL,
municipality INTEGER NOT NULL REFERENCES municipalities(id),
CONSTRAINT unique_city UNIQUE(name, municipality)
);
CREATE TABLE municipalities (
id INTEGER PRIMARY KEY NOT NULL,
name TEXT NOT NULL,
NUMBER INTEGER UNIQUE NOT NULL,
county INTEGER NOT NULL REFERENCES counties(id),
CONSTRAINT unique_municipality UNIQUE(name, county)
);
CREATE TABLE counties (
id INTEGER PRIMARY KEY NOT NULL,
name TEXT UNIQUE NOT NULL
);
EXPLAIN查询... sn.name = ...：
sqlite> EXPLAIN SELECT sn.name, sa.house_number, sa.entrance, pc.postal_code, ci.name, mu.name, co.name, sa.latitude, sa.longitude FROM street_addresses AS sa INNER JOIN street_names AS sn ON sa.street_name = sn.id INNER JOIN postal_codes AS pc ON sa.postal_code = pc.id INNER JOIN cities AS ci ON sa.city = ci.id INNER JOIN municipalities AS mu ON sa.municipality = mu.id INNER JOIN counties AS co ON mu.county = co.id WHERE sn.name = "FORNEBUVEIEN" AND sa.house_number = 13 ORDER BY ci.name ASC, sn.name ASC, sa.house_number ASC, sa.entrance ASC LIMIT 0, 100; addr opcode p1 p2 p3 p4 p5 comment ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- 0 Init 0 91 0 00 1 OpenEpheme 6 6 0 k(4,B,B,B, 00 2 Integer 100 1 0 00 3 Integer 0 2 0 00 4 MustBeInt 2 0 0 00 5 IfPos 2 7 0 00 6 Integer 0 2 0 00 7 Add 1 2 3 00 8 IfPos 1 10 0 00 9 Integer -1 3 0 00 10 OpenRead 7 12 0 k(2,nil,ni 00 11 OpenRead 0 13 0 9 00 12 OpenRead 8 14 0 k(5,nil,ni 00 13 OpenRead 2 9 0 2 00 14 OpenRead 3 7 0 2 00 15 OpenRead 4 4 0 4 00 16 OpenRead 5 2 0 2 00 17 String8 0 4 0 FORNEBUVEI 00 18 SeekGE 7 65 4 1 00 19 IdxGT 7 65 4 1 00 20 IdxRowid 7 5 0 00 21 IsNull 5 65 0 00 22 Integer 13 6 0 00 23 SeekGE 8 65 5 2 00 24 IdxGT 8 65 5 2 00 25 IdxRowid 8 7 0 00 26 Seek 0 7 0 00 27 Column 8 3 8 00 28 MustBeInt 8 64 0 00 29 NotExists 2 64 8 00 30 Column 8 4 9 00 31 MustBeInt 9 64 0 00 32 NotExists 3 64 9 00 33 Column 0 8 10 00 34 MustBeInt 10 64 0 00 35 NotExists 4 64 10 00 36 Column 4 3 11 00 37 MustBeInt 11 64 0 00 38 NotExists 5 64 11 00 39 Column 7 0 12 00 40 Column 8 1 13 00 41 Column 8 2 14 00 42 Column 2 1 15 00 43 Column 3 1 16 00 44 Column 4 1 17 00 45 Column 5 1 18 00 46 Column 0 3 19 00 47 RealAffini 19 0 0 00 48 Column 0 4 20 00 49 RealAffini 20 0 0 00 50 MakeRecord 12 9 21 00 51 Column 3 1 22 00 52 Column 7 0 23 00 53 Column 8 1 24 00 54 Column 8 2 25 00 55 Sequence 6 26 0 00 56 Move 21 27 0 00 57 MakeRecord 22 6 28 00 58 IdxInsert 6 28 0 00 59 IfZero 3 62 0 00 60 AddImm 3 -1 0 00 61 Goto 0 64 0 00 62 Last 6 0 0 00 63 Delete 6 0 0 00 64 Next 8 24 0 00 65 Close 7 0 0 00 66 Close 0 0 0 00 67 Close 8 0 0 00 68 Close 2 0 0 00 69 Close 3 0 0 00 70 Close 4 0 0 00 71 Close 5 0 0 00 72 OpenPseudo 9 21 9 00 73 Sort 6 89 0 00 74 AddImm 2 -1 0 00 75 IfNeg 2 77 0 00 76 Goto 0 88 0 00 77 Column 6 5 21 00 78 Column 9 0 12 20 79 Column 9 1 13 00 80 Column 9 2 14 00 81 Column 9 3 15 00 82 Column 9 4 16 00 83 Column 9 5 17 00 84 Column 9 6 18 00 85 Column 9 7 19 00 86 Column 9 8 20 00 87 ResultRow 12 9 0 00 88 Next 6 74 0 00 89 Close 9 0 0 00 90 Halt 0 0 0 00 91 Transactio 0 0 10 0 01 92 TableLock 0 11 0 street_nam 00 93 TableLock 0 13 0 street_add 00 94 TableLock 0 9 0 postal_cod 00 95 TableLock 0 7 0 cities 00 96 TableLock 0 4 0 municipali 00 97 TableLock 0 2 0 counties 00 98 Goto 0 1 0 00
EXPLAIN查询... sn.name LIKE ...：
sqlite> EXPLAIN SELECT sn.name, sa.house_number, sa.entrance, pc.postal_code, ci.name, mu.name, co.name, sa.latitude, sa.longitude FROM street_addresses AS sa INNER JOIN street_names AS sn ON sa.street_name = sn.id INNER JOIN postal_codes AS pc ON sa.postal_code = pc.id INNER JOIN cities AS ci ON sa.city = ci.id INNER JOIN municipalities AS mu ON sa.municipality = mu.id INNER JOIN counties AS co ON mu.county = co.id WHERE sn.name LIKE "FORNEBUVEIEN" AND sa.house_number = 13 ORDER BY ci.name ASC, sn.name ASC, sa.house_number ASC, sa.entrance ASC LIMIT 0, 100; addr opcode p1 p2 p3 p4 p5 comment ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- 0 Init 0 88 0 00 1 OpenEpheme 6 6 0 k(4,B,B,B, 00 2 Integer 100 1 0 00 3 Integer 0 2 0 00 4 MustBeInt 2 0 0 00 5 IfPos 2 7 0 00 6 Integer 0 2 0 00 7 Add 1 2 3 00 8 IfPos 1 10 0 00 9 Integer -1 3 0 00 10 OpenRead 0 13 0 9 00 11 OpenRead 1 11 0 2 00 12 OpenRead 4 4 0 4 00 13 OpenRead 3 7 0 2 00 14 OpenRead 5 2 0 2 00 15 OpenRead 2 9 0 2 00 16 Rewind 0 63 0 00 17 Column 0 1 4 00 18 Ne 5 62 4 (BINARY) 6c 19 Column 0 5 6 00 20 MustBeInt 6 62 0 00 21 NotExists 1 62 6 00 22 Column 1 1 9 00 23 Function 1 8 7 like(2) 02 24 IfNot 7 62 1 00 25 Column 0 8 10 00 26 MustBeInt 10 62 0 00 27 NotExists 4 62 10 00 28 Column 0 7 11 00 29 MustBeInt 11 62 0 00 30 NotExists 3 62 11 00 31 Column 4 3 12 00 32 MustBeInt 12 62 0 00 33 NotExists 5 62 12 00 34 Column 0 6 13 00 35 MustBeInt 13 62 0 00 36 NotExists 2 62 13 00 37 Column 1 1 14 00 38 Copy 4 15 0 00 39 Column 0 2 16 00 40 Column 2 1 17 00 41 Column 3 1 18 00 42 Column 4 1 19 00 43 Column 5 1 20 00 44 Column 0 3 21 00 45 RealAffini 21 0 0 00 46 Column 0 4 22 00 47 RealAffini 22 0 0 00 48 MakeRecord 14 9 7 00 49 Column 3 1 23 00 50 Column 1 1 24 00 51 Column 0 1 25 00 52 Column 0 2 26 00 53 Sequence 6 27 0 00 54 Move 7 28 0 00 55 MakeRecord 23 6 29 00 56 IdxInsert 6 29 0 00 57 IfZero 3 60 0 00 58 AddImm 3 -1 0 00 59 Goto 0 62 0 00 60 Last 6 0 0 00 61 Delete 6 0 0 00 62 Next 0 17 0 01 63 Close 0 0 0 00 64 Close 1 0 0 00 65 Close 4 0 0 00 66 Close 3 0 0 00 67 Close 5 0 0 00 68 Close 2 0 0 00 69 OpenPseudo 7 7 9 00 70 Sort 6 86 0 00 71 AddImm 2 -1 0 00 72 IfNeg 2 74 0 00 73 Goto 0 85 0 00 74 Column 6 5 7 00 75 Column 7 0 14 20 76 Column 7 1 15 00 77 Column 7 2 16 00 78 Column 7 3 17 00 79 Column 7 4 18 00 80 Column 7 5 19 00 81 Column 7 6 20 00 82 Column 7 7 21 00 83 Column 7 8 22 00 84 ResultRow 14 9 0 00 85 Next 6 71 0 00 86 Close 7 0 0 00 87 Halt 0 0 0 00 88 Transactio 0 0 10 0 01 89 TableLock 0 13 0 street_add 00 90 TableLock 0 11 0 street_nam 00 91 TableLock 0 4 0 municipali 00 92 TableLock 0 7 0 cities 00 93 TableLock 0 2 0 counties 00 94 TableLock 0 9 0 postal_cod 00 95 Integer 13 5 0 00 96 String8 0 8 0 FORNEBUVEI 00 97 Goto 0 1 0 00
答案 0 :(得分：3)
documentation表示LIKE需要不区分大小写的索引：
CREATE INDEX ci_name ON street_names(name COLLATE NOCASE);
EXPLAIN QUERY PLAN SELECT ... sn.name LIKE "FORNEBUVEIEN" ...;
0|0|1|SEARCH TABLE street_names AS sn USING COVERING INDEX ci_name (name>? AND name<?)
...
或者，使用GLOB可以使用区分大小写的索引：
EXPLAIN QUERY PLAN SELECT ... sn.name GLOB "FORNEBUVEIEN" ...;
0|0|1|SEARCH TABLE street_names AS sn USING COVERING INDEX sqlite_autoindex_street_names_1 (name>? AND name<?)
...
答案 1 :(得分：0)
我不是一个sqlite专家，但在任何SQL方言中，LIKE永远不会像=一样快。但也许您可以重新排列查询以优化它：
SELECT sn.name, sa.house_number, sa.entrance, pc.postal_code, ci.name, mu.name,
co.name, sa.latitude, sa.longitude
FROM
street_addresses AS sa
INNER JOIN street_names AS sn ON sa.street_name = sn.id
AND sn.name LIKE "FORNEBUVEIEN"
INNER JOIN postal_codes AS pc ON sa.postal_code = pc.id
AND sa.house_number = 13
INNER JOIN cities AS ci ON sa.city = ci.id
INNER JOIN municipalities AS mu ON sa.municipality = mu.id
INNER JOIN counties AS co ON mu.county = co.id
ORDER BY ci.name ASC, sn.name ASC, sa.house_number ASC, sa.entrance ASC
LIMIT 0, 100;
我的想法是，通过尽早强制进行评估，可以解析更少的数据。当然，如果优化器足够智能，它就已经优化了访问路径。