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104 lines
2.3 KiB
Go
104 lines
2.3 KiB
Go
package fts5
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import "strings"
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// ConvertQuery transforms a Google-like query into a SQLite FTS5 one.
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func ConvertQuery(query string) string {
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out := ""
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// List of tokens which won't be automatically quoted in the output query.
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passthroughTokens := map[string]bool{
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"AND": true,
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"OR": true,
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"NOT": true,
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}
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// Whitespaces and parentheses are term separators outside explicit quotes.
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termSeparators := map[rune]bool{
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' ': true,
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'\t': true,
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'\n': true,
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'(': true,
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')': true,
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}
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// Indicates whether the current term was explicitly quoted in the query.
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inQuote := false
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// Current term being read.
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term := ""
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// Finishes the current term and write it to the output after quoting it.
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closeTerm := func() {
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if term == "" {
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return
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}
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if !inQuote && passthroughTokens[term] {
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out += term
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} else {
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// If the term has a wildcard suffix, it is a prefix token. We make
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// sure that the * is not quoted or it will be ignored by the FTS5
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// tokenizer.
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isPrefixToken := !inQuote && strings.HasSuffix(term, "*")
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if isPrefixToken {
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term = strings.TrimSuffix(term, "*")
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}
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out += `"` + term + `"`
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if isPrefixToken {
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out += "*"
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}
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}
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term = ""
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}
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for _, c := range query {
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switch {
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// Explicit quotes.
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case c == '"':
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if inQuote { // We are already in a quoted term? Then it's a closing quote.
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closeTerm()
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}
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inQuote = !inQuote
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// Passthrough for ^ and * when they are at the start of a term, to allow:
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// ^foo -> ^"foo"
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// "foo"* -> "foo"*
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case term == "" && (c == '^' || c == '*'):
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out += string(c)
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// Passthrough for FTS5's column filters, e.g.
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// col:foo -> col:"foo"
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case !inQuote && c == ':':
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out += term + string(c)
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term = ""
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// - is an alias to NOT, but only at the start of a term, to allow
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// compound words such as "well-known"
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case c == '-' && term == "":
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out += " NOT "
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// | is an alias to OR.
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case !inQuote && c == '|':
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closeTerm()
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out += " OR "
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// FTS5's + is ignored because it doesn't bring much to the syntax,
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// compared to explicit quotes.
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case !inQuote && c == '+' && term == "":
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break
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// Term separators outside explicit quotes terminates the current term.
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case !inQuote && termSeparators[c]:
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closeTerm()
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out += string(c)
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default:
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term += string(c)
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}
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}
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closeTerm()
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return out
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}
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