Documentation
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Overview ¶
Package dialect describes the SQL language differences between the databases Momo supports. A Dialect says what the SQL *language* can express; what a particular connection driver can do (COPY, batching, extension loading) is a separate, driver-level capability.
Index ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
This section is empty.
Types ¶
type Dialect ¶
type Dialect struct {
Name Name
// Flavor is set on MySQL dialects only.
Flavor Flavor
// MaxParams is the largest number of bind parameters a single statement
// may carry. PostgreSQL's wire protocol limit is 65535; SQLite's
// default SQLITE_MAX_VARIABLE_NUMBER is 32766 since 3.32.0.
MaxParams int
// MaxInList caps the values in one typed IN or NOT IN list. Zero means no
// cap. momo.WithMaxInList sets it on the per-DB copy of the dialect.
MaxInList int
Returning bool // INSERT/UPDATE/DELETE ... RETURNING (SQLite >= 3.35)
InsertReturning bool // INSERT ... RETURNING only (MariaDB >= 10.5); Returning stays false there
OnConflict bool // INSERT ... ON CONFLICT
OnDuplicateKey bool // INSERT ... ON DUPLICATE KEY UPDATE
Locking bool // SELECT ... FOR UPDATE / FOR SHARE / SKIP LOCKED / NOWAIT
NullsOrdering bool // ORDER BY ... NULLS FIRST|LAST (SQLite >= 3.30)
DefaultInUpdate bool // UPDATE ... SET col = DEFAULT
DefaultInValues bool // INSERT ... VALUES (DEFAULT)
RecursiveCTE bool
RowValues bool // (a, b) IN ((?, ?), ...) and (a, b) > (?, ?)
Savepoints bool
IsolationLevels bool // BEGIN with an isolation level
TransactionalDDL bool // DDL can be rolled back
ILike bool
Merge bool // MERGE statement
WindowFunctions bool
// Vector describes vector storage, distance metrics and ANN indexes.
Vector VectorCaps
}
Dialect is immutable after construction and safe for concurrent use.
func MySQLFlavor ¶
MySQLFlavor returns the MySQL-family dialect for the given flavor, or nil for an unknown flavor. Every call returns a fresh value.
MySQL Community has VECTOR storage from 9.0 but no distance function, so it lists no metrics and no index. MariaDB 11.8 has VEC_DISTANCE_EUCLIDEAN and VEC_DISTANCE_COSINE and VECTOR INDEX, and supports INSERT ... RETURNING but not UPDATE or DELETE ... RETURNING. A server-version gate in migrate/mysql rejects VECTOR on MySQL 8.4.
func (*Dialect) AppendIdent ¶
AppendIdent appends a quoted identifier. MySQL uses backticks; the other dialects use the SQL standard double-quote form. Embedded quote characters are doubled. Dotted names are NOT split: callers quote each part separately.
func (*Dialect) AppendPlaceholder ¶
AppendPlaceholder appends the n-th (1-based) bind placeholder.
func (*Dialect) QuoteIdent ¶
QuoteIdent returns a quoted identifier.
type Flavor ¶
type Flavor string
Flavor distinguishes servers that share the MySQL dialect. It is set on MySQL dialects only.
type Metric ¶
type Metric string
Metric names a vector distance metric.
const ( MetricL2 Metric = "l2" // <-> on PostgreSQL; vec_distance_l2 on SQLite MetricInnerProduct Metric = "ip" // <#> (negative inner product) on PostgreSQL only MetricCosine Metric = "cosine" // <=> on PostgreSQL; vec_distance_cosine on SQLite MetricL1 Metric = "l1" // <+> on PostgreSQL; vec_distance_l1 on SQLite MetricHamming Metric = "hamming" // <~> on PostgreSQL; vec_distance_hamming on SQLite (bit vectors) MetricJaccard Metric = "jaccard" // <%> on PostgreSQL only )
type VectorCaps ¶
type VectorCaps struct {
Storage bool // vector column types can be declared
Metrics []Metric // distance metrics this dialect renders
Indexes []string // ANN index methods available: "hnsw", "ivfflat", "vector"
}
VectorCaps describes a dialect's vector support.
Source Files